Hi,
This will come as two questions:
I've been looking to start up a campaign and my players made the characters. Basically I have no healer or fighter class. We have a ranger(archer), thief and bard. So I've came up with the idea of companions(Ala Dragon Age). Basically the players can select a companion to help them in their quests. They will be roleplayed by me but rolled by the players. The companions will all have their backgrounds and quests the characters can put effort into(or not) and will have no impact in said game except the boost in HP and healing potency of the group basically. Is it almost DMPC? And if it is, what should I do to avoid it becoming asking the DM PC's to solve everything.
At the beginning of the campaign, the PCs know a very important wizard who sends them back in the past to save the future(pretty much like Xmen) and they will have to meet said wizard in the past to avoid the crappy future. How should I play this to avoid the characters to use the wizard extensively. I tought about him as a NPCs who somethings will act around key plot points but pretty much stays in the background the rest of the time.
Thanks for any advice or tips
Some suggestions:
To stop the dreaded DMPC! syndrome. Which I think is unlikely as this more becomes a problem when DM's are trying to get the enjoyment of playing at the same time as running the game.
1) Just plainly point out the reason the character is to bulk up the characters with healing, not to be a DMPC or a plot/solution dispenser.
2) Have the companion be a very loyal but passive personality. No great on personal initative but very willing to help in a pinch.
3) Let the players control them, either collectively or taking turns. It might drop a bit from in-character immersion but have them willing to follow orders... perhaps to the verge of being a bit reckless in doing so.
If a dispute occurs over what one they should do... then either choose for the NPC based on reasonableness or just roll a dice. (For extra amusement, have the NPC themselves pull out a coin or dice and rolling it to decide at the time)
4) You can have them occasionally chip in if the players are completely stalled but basically assume they're a bit vacant minded most of the time.
Thalies wrote:
What I ended up doing for my kids during this Basic campaign was, since they were half a team, (Fighter and Rogue,) I kept the Cleric on hand and when they needed help, she "happened" upon them, now she's traveling with them and if we weren't near the end, I'd just have her head out again, but I figure I'll keep her around as she gets them RPing more.
The bard and the ranger actually can heal. they'll be fine.
When I DM'd a long time ago, I used to plant my NPCs into the party to "help" them.
I found out I was doing it just becasue I really wanted to play more than DM.
I also found I was using those NPCs to railroad the party, even subtly.
Since I've been DMing again, I don't put NPCs with the party (unless it's plot specific, but then such NPCs have their own agendas).
I enjoy this more. It's a lot of fun to sit back and watch the party figure out how they're going to survive an encounter with the resources they do have.
Embrace what DMing is. It's a lot of fun by itself. It's a different kind of fun from playing, and that's actually half the fun. 
I ran "companions" or mercenaries during 4e for one of my groups and it seemed to have gone pretty well. I had to do a lot of homebrewing but in the end it worked out. In essence, the NPCs could be "hired" and essentially controlled by the PCs. Although they had decent party composition, I think the players really wanted to feel like they controlled a small army of troops and what not, so I just went with it.
In general, out of combat, the NPCs remained very passive, once in a while perhaps making a suggestion here or here. They did not make Perception checks, or skills checks, unless it was something they were specialized in and hired for those reasons.
In combat, I allowed the player characters to use a Quick/Bonus Action to give their NPC a rough command - like "attack those goblins" or "defend me", I even wrote out specific types of "formation" or "stances" the NPC would generally take if they were not given orders. They were not stupid robots, but instead, generally fought for self preservation while letting the super characters do most of the work. The NPCs did not mind mopping up. A Bonus Action was not needed each turn to micro-manage the NPCs. Likewise, a Bonus Action could be taken to command an NPC to do a "special attack or action". 4th Ed had a lot of those and I just mapped out a few for each NPC. NPCs also had morale, often retreated if they were in trouble, or moved to the backline when severely wounded. They would revive each other if need be, and cover each other especially if within a squad. The PCs generally "controlled" the NPCs during combat, but time to time the NPCs would have a mind of their own.
The players seemed to have fun with it. One Warlord character actually had a squad of NPCs around and basically led a small unit during most of the combat encounters. Another player's character ended up marrying his NPC companion (and they retired the characters ~ he suffered serious wounds and had to get resurrected).
Overall though, i made sure all the players were cool with the concept of having NPC companions for the group and understood that they potentially could "slow" down combat sequences, which in the end, they actually didn't as the players were fast with their decisions and dice rolls.
It sounds like they have a sneaky party, working a lot from range (I assume the thief use a ranged weapon quite a lot). I think that giving them interesting terrain, places to hide and opportunities to sneak around or ambush encounters rather than charging the party should be better off without a meat shield/tank. With both a bard and a thief in the party it should also be possible to talk their way out of encounters. And as mentioned: both rangers and bards can select healing spells.
In short: avoid encounters where they need a meat shield and can compensate by stealth, movement and social skills and they should be perfectly fine is my guess.