If you listen to the experts (the guys who run it/coach it effectively) talk about the cover 2, they pretty much all say it takes 2-3 years to get everybody playing correctly in the system. It really has a lot to do with discipline, much like the west coast offense.
Also , the Cover 2 really has nothing to do with the type of front 4 you utilize.
Ideally, we need to get atleast one guy (DT) with both size AND quickness to make this thing work better.