It's not about the size of the dog in the fight; it's the strength of the dog in the fight. AD proves that. Turner and Desjuan Johnson could learn a ton from AD about how to use leverage and strength to shed blockers.
So long as the players we draft have strength in their upper and lower body, it doesn't matter how big they are. I've seen Albert Haynesworth at 6'4", 330 lbs. get knocked off his ass. I've seen Aaron Donald throw offensive linemen around like they were little kids.
That's all that matters, really. So long as this defensive line can stack up like I think they can, they'll be fine against the run. Edges will have to keep contain, inside linebackers have to not miss tackles and plug in the holes, but I think they can.