In gestalt, you should really be shooting for much higher--dual, triple threats, great saves, etc. etc.
Also, Duelist? Come on! Shadowdancer?
Anyway, switch the rogue side to something from tome of battle, and then use the other side for the various fun (rogue, swash, etc.)
Also... you have a ton of weak feats (I think some are prereqs, but they are still weak feats!)
Point Blank Shot, Weapon focus (dagger), Dodge, Mobility, Far Shot, Weapon Specialization... Also, in gestalt, your will should be WAY higher!
Gestalt is all about reducing weaknesses, so you can pull your weight...
But gestalt means a lot of things. The idea, to me of gestalt is this:
You have two, three, or even just one character. These characters should be VERY survivable, and able to handle multiple party roles, both in and out of combat. These characters should be more powerful than an average single-classed character, and Gestalt is a way to make that easy to do.
So lets take some roles, as an example:
1.) Tough meleeist/defender
2.) Primary arcane caster / battlefield control
3.) Melee/Ranged striker / stealth and trap skills
4.) Primary divine caster / buffer / damage mitigator/healer
Now, these are the four main "threats" of 3.5e. You have chosen 1 and 3 as your foci. That's fine. But there are better ways to focus on that, even if you have to take one side all the way to 20.
Also, i suppose i should justify some of my choices here. First of all, Invisible Blade is what the whole thing is based around, so the feats Weapon Focus(dagger), Point Blank Shot, and Far Shot cannot go anywhere. Second, duelist has good synergy with a class that adds thier int mod to their damage, and their AC, and Elaborate Parry is really nice in those moments you need high AC. So the Feats Dodge and Mobility stay. Now, i have 3 class levels the play with, what can i do with that...well, my DM is an @#$%^$! about concealment, so i will remove that question altogether, by having hide in plain sight, fastest way to do that? Shadowdancer. Honestly, i considered taking 2 levels of it for Darkvision. the 2 fighter levels? i like the base attack, and 2 points of damage every attack sound tasty to me. Yes, i could have used something from the Tome of Battle, I could have probably talked the DM itno allowing guild thief and got a couple of extra dice of sneak attack in the process, not to mention the extra bluff goodness, but the character wasn't a guild thief, or a Holy Liberator, he was a Fighting Rouge, so i too the fighter levels. Hope that clears up some of the questions about the decisions made during this character's designing
Add tome of Battle to your books list, if possible.
Get some Swordsage in there.
Add Complete Scoundrel to your books list.
Get the Daring Outlaw feat.
Remove all duelist levels.
Remove Shadowdancer Levels.
Consider making the character two-weapon-fighting focused.
I would also consider staying away from the bluff to feint thing in combat... even if you invest REALLY heavily in it, it really doesn't help too much.
Can you explain why it doesn't help, Uncanny Dodge is one of my greatest enemies, and rightly so! if you flank someone who has uncanny dodge, you had better hope for some reason the abandoned that class 4 levels ago, because if they didn't you can't flank them, and as far as using hide, that doesn't work regardless what level they are, the don't suffer the Sneak attack, now, if you are bluffed, and have uncanny dodge, you still lose your dex mod, and thus get hit for the SA. I think this is much more adaptable than flanking, and much more reliable than being invisible, or relying on hide to get sneak attack.
Rogue brings high number of skills, sneak attack damage and evasion, while fighter brings massive amount of combat feats and BAB
I would try to make a build to hit them always flat flooted, and you have yourself a really decent build. If you can accomplish that and get yourself a good number of attacks, I would say it really is a decent optimized build even.
I would recommend you look at the Factotum of War build. It has similar synergy, except I would prefer it slightly because it has good stat synergy. (Int)
Fighter is sometimes considered underpowered. That's not true, but it can be because the feats can be limiting if not really well planned/synergized.
Warblade brings quite a few maneuvers to the table. I personally think maneuver combos are a lot more fun than passive feats. You can see the many combos here Tome of Battle: Tricks/Combos/Library, but the combos in the Factotum of War are already well tailored towards the build it has.
For a non caster build, it's incredibly strong. Factotum is as much if not more of a skill monkey than the rogue. Especially with int as a main stat, . . . you will have a lot to choose from.
When I do a non-gestalt, I usually end up with swash3/fight2/rogueX, with some of these feats, and a focus on kukris.
telling blow (only if you build a character to take advantage of this though!)
two weapon fighting
improved buckler defense
improved two weapon fighting
Craven
Iron Will
Combat Reflexes
Vexing Flanker
Sneak Attack of Opportunity (dragon magazine version)
Darkstalker
Parrying Shield
Staggering Strike