I'm going to start with the AC chain because that's really what started the whole mess. I've always been bothered by the way AC is presented in the core rulebooks. "If you roll this number or less on your attack roll you miss. If you beat it you hurt them." Simple? Yes. Realistic? Definitely not. I can accept that explanation for a defender in leather armor, but consider the case of Bracers of Armor. The description states that the Bracers generate a "magical field of force" which completely encompasses the wearer. If the field has no chinks or breaks into which a weapon can be slipped how, exactly, does a high attack roll hurt them? Does the weapon punch through the field? If so, shouldn't it have its damage reduced based on the strength of the field it passed through? Then there's full plate. That presents a whole other set of problems. I can deal with a rapier finding its way into the slits and joints of plate mail...but what about a greataxe? Surely THAT isn't being deftly guided into breaks in the armor?
My solution to this problem works to a certain extent but it tends to slow things down quite a bit...and it requires a lot of set up work. If you've got ideas on how to do this better, I'd be interested in hearing them. My idea consists of two parts: the AC chain, and the armor damage rules.
Part 1: The AC Chain
The AC chain is actually a really simple idea which I still make use of for determining the outcome of attack rolls by both PCs and NPCs. Essentially, an AC chain is a point-by-point chart detailing where a character's total AC comes from. The reason this is important is that it lets you know what (if anything) an attacker did with his attack roll. Basically, you can compare an attack roll with the chart for a given defender and see that the attacker completely missed his target, or the defender dodged out of the way, or the attacker's claws raked across the front of the defender's breastplate. The AC chain itself is created simply by applying a ranking system to the various AC bonuses a character can receive. A character with every type of bonus (that I can think of right now) would look like this:
Base AC: A number in this range misses without the defender having to take any action.
Luck/Divine Bonus: Essentially an extension of Base AC. An attack roll that falls in this range requires no action on the part of the defender to miss.
Dex/Dodge Bonus: This attack would've struck the defender had he not been nimble enough to get out of the way.
Shield Bonus: This attack came too quickly for the defender to get out of the way, but slowly enough that he was able to block with his shield.
Armor Bonus: This attack gave the defender no chance to protect himself. All that saved him from damage was his armor.
Nat Armor Bonus: This attack bypassed all other defenses and was only stopped by the defender's natural toughness.
Thus, a paladin with a few magic items wearing full plate would look like this:
0-10 Base
11-12 Divine
13 Dex
14-15 Shield
16-23 Armor
An attacker who rolls a 15 will strike the paladin's shield, while a 17 would strike the paladin's armor. The net effect is the same as the regular AC rules, but it can help players (and the DM!) to visualize how a combat is unfolding.
Part 2: Armor Damage
Ever noticed how almost no one ever chooses to wear heavy armor? After all, why should you when you can receive the exact same protection by having a high Dexterity score and wearing light or no armor? Why burden yourself with 40-plus pounds of dead weight? It's because of this question (and a wistful urge to go back to the days when playing a knight in shining armor was still cool) that I've tried to even out the playing field between heavy and light armors. Be warned, however, that the following variant rules get pretty complex.
First, assign a hardness to each type of armor based upon its material composition. I strongly recommend using hardness 1 for leather and like materials and a hardness of 5 for steel. I know this doesn't match up with the hardnesses presented in the various core rulebooks but trust me, hardness 10 on full plate leads to absolutely ridiculous battles. For magical armor, add 1 to the hardness of the armor for every point of enhancement bonus.
Second, assign a damage threshold to each type of armor based upon its material composition and its construction. Damage threshold represents how many HP from a single blow a piece of armor can absorb before it is breached. I recommend using twice the armor's hardness for this value. Thus, leather would have a DT of 2 while steel would top out around 10.
Third, decide how many hit points a given suit of armor should have. The way I liked the most for doing this was to multiply an armor's AC bonus by 10. Thus, full plate has 80 HP, half plate has 70 HP, and so on. For magical armor, add 10 to the HP of the armor for every point of enhancement bonus.
Fourth, decide on a coverage rating for the armor. I've found that coverage ratings work best when you go by thirds of the body. In this way, breastplates and shirts have a CR of 2, shirts and greaves have a CR of 4, and full-body armors like full plate and full chain have a CR of 6. I arrived at these numbers after a lot of play testing. You're obviously welcome to try your own out, but going much higher than this tips the scales way too far in favor of heavy armor.
Finally, total up the AC of the defender and apply the armor's coverage rating to it. An armor's coverage rating can be looked at as a sort of phantom AC bonus that's added to the top of the AC chain. Whenever an attacker rolls higher than a defender's actual AC but below his phantom AC the weapon deals damage directly to the defender's armor and has a chance to punch through to the person wearing it. (Technically the attack should damage the armor on any roll that falls on the Armor Bonus section of the defender's AC chain but this tends to lead to armor falling apart after only a few fights.)
To determine if an attack is capable of punching through a defender's armor roll damage as normal, then subtract the armor's hardness from the damage roll. The resulting damage is subtracted from the HP of the armor up to its damage threshold. Anything left after that is dealt directly to the defender and is then subject to any damage reduction the character would normally be entitled to.
This adds a final category onto the end of our AC chain:
Phantom AC: An attack roll which falls within this category strikes with enough force to damage the armor of the defender and may (depending upon the force of the blow) punch through to damage the defender.
Thus, our paladin from before would have an AC chain that looks like this:
0-10 Base
11-12 Divine
13 Dex
14-15 Shield
16-23 Armor
24-29 Phantom
An attack roll of 27 would hit the paladin's armor with enough force to do damage. A damage roll of 16 would have its first 5 points negated by the armor's hardness. The next 10 points of damage would be absorbed by the armor's HP (reducing it from 80 to 70) and the final point would be dealt to the paladin himself. A few more blows like that and his armor will be nigh-unto useless.
Which leads us to the next logical step in this equation. As armor takes damage its effectiveness will obviously decrease. There are any number of different ways to describe this change in game terms, but I think the simplest and most realistic would be to base it off of a rough percentage. When armor reaches 50% of its total hit points reduce its AC bonus by half (rounding up) and apply a –2 to its armor check penalty. When armor reaches 0 hit points reduce its AC bonus by half again (round up; this will result in a net loss of 75%), apply an additional –2 to its armor check penalty (for a total of –4), subtract 2 from its maximum Dexterity bonus, and reduce its coverage rating by 1 step. These penalties represent the loss of mobility and coverage that come from severe damage to a suit of armor.
Yes, this means that a given suit of armor will, in a drawn out fight, be ruined fairly quickly. I recommend allowing PCs to make untrained (or trained, if they’ve got the tools and skills) repair checks. Based upon the amount of time and materials available, I recommend allowing repair checks to fix anywhere from 1 HP per 5 points rolled on a repair check to 1 HP per 1 point rolled on the check. That’s totally a DM-discretion kind of a thing, but I don’t recommend allowing a character to repair more than 50% of a suit of armor’s HP without proper training or tools, and I’d suggest making each check after the first progressively more difficult, forcing untrained characters to seek out the services of an armorsmith when one is available.
This last issue that I’ll address regarding the armor damage rules is one that hadn’t occurred to me until one of my players brought it up in play testing. Under the current AC rules there’s no system in place for layering armor, but with armor damage rules in effect the practice becomes much more tempting. Here’s my take on it.
First off, common sense should rule the day. You can’t wear a breastplate under a suit of full plate, but you could wear a chain or leather shirt. Even if you could, the added weight of the second suit of heavy armor would essentially immobilize most characters. To that end, I recommend allowing only light armors like padded, leather, and chain shirts to be worn underneath other armor (I would also disallow wearing 2 suits of light armor…no padded-beneath-leather combos). Normal bonus-stacking rules apply…which is to say, they don’t. A person wearing a leather shirt under half-plate would use the armor bonus from the half-plate alone. Similarly, the phantom AC bonuses from the two suits of armor overlap rather than stacking. Armor check penalties should stack and then have an additional –2 added to them. The maximum Dexterity bonus of the most restrictive armor should be used and then reduced by 2. This means that half-plate over leather provides the following stats: AC 7 and Max Dex –2. The benefits of wearing layered armor come into play when the defender’s armor suffers a hit. Let’s go back to the example of the paladin used above, but this time we’ll say he’s wearing leather armor under his full plate. His armor stats would thus be AC 8, Max Dex –1. Plate: CR 6, Hardness 5, DT 10, HP 80; Leather: CR 2, Hardness 1, DT 2, HP 80. His AC chain now looks like this:
0-9 Base (minus 1 for a low Dexterity)
10-11 Divine
12-13 Shield
14-22 Armor
23-24 Phantom (leather and plate)
25-28 Phantom (plate)
Our paladin is now slightly easier to hit in combat due to his reduced maneuverability; however, if he does take a hit it’s almost guaranteed not to cause him any physical damage. Say our attacker rolls a 24. This strikes with enough force to damage the paladin’s armor. The attacker rolls a 22 for damage. The first 5 points are absorbed by the plate’s hardness, then the next 10 points are dealt to its HP. This means that 7 points of damage made it through the plate armor. Next, the leather’s hardness absorbs 1 point of that damage and then 2 points are dealt to the leather’s HP, leaving 4 points of damage unaccounted for. Our paladin takes a meager 4 points of damage and is now ready to return fire. His armor now has 70 HP (plate) / 18 HP (leather).
Finally, we return to the Bracers of Armor and other similar items and effects like Mage Armor. I recommend treating these effects exactly like enhancement bonuses to normal armor but without the armor to back them up and without a hit point total to subtract damage from. Essentially, the hardness and damage threshold of these types of armor are the same thing. This way, Bracers of Armor +2 would have the following stats: AC +2, Hardness 2, Damage Threshold 4, and CR 6.
Like I said way back at the beginning, these rules are deeply involved. I don’t know how much use you’ll get out of them (especially the armor damage rules), but I’d be interested in hearing your opinions on them. I’m really fond of all of them, but the armor damage rules proved to be a little bit too cumbersome for my particular gaming group. The armor damage / phantom AC rules really add to the way heavy armor plays. In my mind it gives it a lot more value, making it much more realistic. Using these rules a knight in full plate is literally a walking tank…and isn’t that what full plate is really all about?
There's no real rule that state the character blocking attacks with is own weapon. In fact, when in combat, there's two defense that overpass any others. Firstly, if you are equipped with a shield, you block 90% of the attacks with it. The shield is designed to block attacks and this is the easiest way to do it. In fact, in real combat, the shield give more "AC bonus" than an armor has you block more hits that your armor protects you from an unblocked hit. Secondly, when you don't have a shield, you black most of the attacks with your own weapon. In rule system, maybe the base AC of 10 figures that part, but in that way, a character without any weapon (if not having the Improve Unarmed Fight feat) should not have a base AC of 10 has he is not ably to parry any attacks (the only bonus he should get is his dex bonus). If not, the only rule that could figure the "parry" in combat is while choosing Full-defense or Combat defensively.
In a realistic fight, fighters are always moving throughout defensive-offensive state. In fact, you are more than 60-80% of the time "on defense". You try to parry all the attacks and only attacks a few times to not get overrun by your opponent. The only time you try an attack is when your opponent make a mistake in his defense. For example, if he tries to hit you, leaving a undefended spot behind his right shoulder and you see that you will be able to block his attack, you will then try to counter-attack him trying to hit the spot. Sometime you hits, sometimes you don't (here come the BaB witch mean combat experience or the "dex or dodge bonus" which represent the ability to dodge attack that pass ALL the other defenses, except the armor).
In Neverwinter Night, there is a new feat called Parry which represent well the real combat. Protagonists should always "fight defensively" and make a "parry check". If they succeed to block an attack leaving a undefended spot in the opponent's defense, then he will try to strike.
I have no good solution for that. D20 combat system is mostly good but not realistic and it isn't designed to be realistic. Adding more realism to that kind of system makes it slower and more complex. (I hate being forced to look at tables to see what kind of damage the attack did, were it was placed, etc, etc, etc.)
I only use the base D20 combat system and just add more descriptions to the attacks. For example, if a creature have 18 of AC (large shield, scale mail, +2 dex bonus) and a character tell me "17, does it hurt the creature?" I answer: "You swing your weapon trying to hit a undefended leg spot but the creature manage to block your attack with is shield at the last time".
Effectively a 20th level Fighter is as easy or hard to hit as any Commoner given the same equipment. Disregarding certain feats like Expertise and Dodge and the like, money determines your AC.
I have been playing a RPG a couple of years ago which had a skillbased system for attacks and defense which I thought was pretty good. Let me try to introduce it in not so many words.
It had a skill for each "weaponfamily" like swords, bows, blunt weapons etc. etc. Out of a set of three Stats a base attack and base defense was calculated. Stats in that contributed to these bases were, among others Strength and Dexterity. On top of these bases one could assign the skillpoints. Skillpoints, depending on the class one was, ranged from -18 to +18.
So lets say one has an attack base of 7 (that was a good score for low- to mid-level characters) and also a defend base of 7. Let’s assume the character in question now has 8 points in the swordskill. He could now permanently assign those 8 skillpoints on top of his base values. Once assigned no changes could ever be made again. Only new gained points, when leveling up could be distributed again.
Depending on how one would like to fight--more on the attacking or more on the defending part--he might chose to put 5 points on his attack value and the remaining 3 on defense. That left the character with an overall attack value of 12 and a defense value of 10. He could have gone 15/7 as well, or 7/15 whatever he liked best. Keep in mind that the distribution was once and for all permanently.
Now in this system, rolling low was good. Not like in D&D where high is good. In a fight the attacker would roll a d20 and if his roll was lower than his attack value he would have hit. In theory. Because now the defender gets his chance to defend. He rolls a d20 as well and if he rolls lower than his own defense value he has parried the blow. If not, the attacker would have made actual contact with his weapon, dealing damage.
Armor in that system provided damage reduction rather than defensive bonus. Also the damage weapons dealt was very different from D&D and much less dependant on Strength scores. You need to have very high Strength to get an increase in damage. A longsword, for instance, dealt 1d6+4 base damage and only if one had a strength of 16 or more (16 was quite high level in that system) one would receive a bonus to damage dealt.
Shields provided a so-called weapon comparison bonus. Weapon comparison were two values that each weapon had, which determined how good a weapons was for attack and defense.
A greatsword or heavy warhammer for instance had great attack values. They have a large weight, great momentum and as such are hard to parry. But that force and momentum also lets you have a hard time to bring the weapon in position to parry a blow fast. So they had pretty low defense values.
Before each fight the two combatants had to compare (that’s why weapon comparison values) the attack/ defense values of their weapons and then received certain bonus or penalty to their attack or defense. Shields improved your defensive weapon comparison value and therefore made it easier to block a blow.
That’s the system in short... still a rather long posting. I liked it pretty much as it was more about skill than about money. It was definitely slower than the D&D system, as every attack needed two rolls only to determine hit or miss and on top of that, two fighters of high level could battle each other for hours without actually hitting each other, Attack.. Parry... Attack... Parry. Well there were certain "moves" that would allow you to do attacks that lowered the defenses of your opponent but still it could take long and a few house rulings on exhaustion during a fight had to be made.
Btw. I want to mention, that the duration of a round in both systems differ. A D&D combat round is 6 seconds long, the DSA rounds were IIRC only one half or even one third of that. That's why you are entitled to roll out your parries in DSA, while in D&D the period of 6 seconds includes parrying, feinting, dodging, aso. so the result of a successful or failed attack in D&D may cover several DSA combat rounds and their final outcome. IMO it is a matter of taste which one you like best, D&D combat is more stylized and streamlined, while DSA combat is a tad bit more realistic and detailed.
The above mentioned revision als introduced rules taking into account the effectiveness of certain weapons (piercing, bludgeoning, slashing) regarding certain types of armor. I see the development of weapons and armor as somewhat interdependent: the first fighters used light armor like hide armor and the like to protect themselves from attacks with short swords, light clubs, aso. Then somebody thought how cool it was to have metal armor to more or less negate and deflect attacks from those weapons more effectively. His opponent in turn created new weapons which would be more effective against that new kind of armor, aso. ad infinitum.
This is why I used DR/piercing, slashing, and/or bludgeoning for my armor, instead of AC.
One thing, though... I would recommend that when using blunt weapons, that hits against shield or armor somehow penetrate. After all, the point of weapons like maces was to deliver blunt force trauma through a suit of armor.
Good concepts overall.
You have no base armor bonus, so no 10.
You roll your base armor on a D20, adding +1 for being proficient with a weapon in your hand, and +2 for duel wielding, +3 for a weapon and shield, and +2 for a shield alone.
So your base armor with a sword-and-board fighter is anywhere between 4 and 24. Next you figure in your dex bonus as normal, lets call this fighter's dex 13, he gets +2. After that, his armor is a +1 breastplate so he gets an additional +6. He has no divine/natural or deflection bonuses, etc.
Our fighter's current AC looks like this:
1d20+12. He can have anywhere between 13 and 23 AC, reasonably obtained at level 3 or so, since he has a magic armor.
Now we move to the attacking side, which is where the major change is. First off, this system voids the weapon specialization feats, but does add-on to the focus feats.
You take your character's attack bonus as normal. Lets call it 1d20+7 for our fighter.
Now you take the average of your weapon's damage, our longsword wielding fighter gets a nifty d8. You take half (4.5) and round up. A longsword is worth 5. You add this to your attack roll.
You now have an attack roll of 1d20+12 (It's pure chance that its the same as his AC, I Was making up numbers.
Now, lets see the reasoning behind this:
You take your attack roll, which is also your damage roll. If you tie your enemy's AC you deal 1 point of damage. For every point by which your attack surpasses their AC, you deal one more point of damage, DR and such applying as normal.
This exploits the importance of a high AC, because if you have an AC of +4 and someone has an attack of +10, there’s a good chance that you can take massively more damage from them.
...Actually, its midnight. I can't go in-depth on this, I'm sorry.
But also, for your "layering" idea; a suit of plate armor more or less comes with a layer of chain and a layer of padding underneath it (read the descriptions in the PHB or a any reference on medieval armor).
It seems to work well for me, and it certainly justifies a character being disarmed and rolling on the ground, grabbing a stick and bringing it up just in time to block the enemy's sword.
There was also a feat (prereq: weapon focus) that allowed you to add 1 to the defense score of a chosen weapon while you were wielding it. As far as I'm concerned, that solved the problem and when a player was disarmed, he had to roll on the ground and find a stick to wield to at least get his AC back.
I also use 1d20 instead of allowing them to take 10.
I think the combat expertise and the improved expertise feats in conjunction with BAB already take into account a warrior's ability to defend himself in combat. Yes not all warriors have these feats but I see that as a warrior who chooses to focus more how to attack than how to defend himself. Or if you don't like requiring feats simply give all players these feats for free. That way you can use the existing rules to take into account a person's ability to parry and defend himself without having to add new game mechanics. I just think higher complexity in the combat system just isn't worth the effort. And I know it’s bad to say, but especially when there are many players out there who wouldn't be able to handle more complex game mechanics.