It's not so much the touches, (I think him and Ingram could be close in carries) it's the # of plays Heath is calling for. Now I know that AD is pretty near a superhuman, but as a 32 year old RB, why would you have him on the field for 45-50 plays a game when there's no reason for it?
He even states that Peterson isn't the best pass blocker and we're a passing team. Yes Peterson as a decoy or using him for play action makes sense, but playing him that many snaps doesn't. IMO