In co-op when playing with friends does only the party leader have the ability to choose their character? My friends were telling me they weren't getting a choice never had time to investigate myself really since I've been busy.
I think you have to be like level 2 or 3 before you can start picking your character, that's what I've noticed when I first played it and my friends couldn't choose their characters at first.
Also I think the game randomly chooses heroes or villains for you, I've tried using R2 to change teams, blue or red but once you start the game and it prepares matchmaking it auto gives you blue and then you get a random choice of heroes or villains.