I've watched Phillips' Defense in action and while I admit that it's not the purist 3-4 that the Steelers run, it does operate very similarly. They still depend on the DE/DTs on the outside setting a hard edge. Pass rush comes mainly from the OLB's and any help they can get from the front 3 is secondary and they are used to occupy the Oline to allow a lane for the OLBs to get to the QB.
I just don't see Donald being effective as he was for GW's 4-3 unless they make him a OLB. And with his speed I think he could be. But at a 3-4 DT/DE? I don't buy it. It's not that he won't play the position very well. It's that you don't need an AD talent to man that position. And therefore it is the wrong place to spend HUGE dollars.
Anyway, we'll soon see. No doubt he'll play in game 2, although I'd be willing to bet no more than about 40% of the Defensive snaps.