As I have said before we can all argue who should get what carries and beleive me many have their own idea of who and how the carries should be given. I do think Barber being the better of the 3 in picking up blitzers played a part in the coaches going more with him than the others.
I think as Choice and Felix improve in that area the coaches will have more chances of getting others into the game no matter the situation. I also think they like having Barber physical style come in to wear down on defensive lineman early in games, again I know others feel a different way all I can say is go be a coach then you can rotate guys the way you see fit and others will question your call.