When Coyle came onboard we switched to the 4-3 from the 3-4. Personnel issues still exist from that switch. We added Ellerbe who is more of a 3-4 ILB than a 4-3 MLB, Wheeler sucks in any scheme, Vernon and Jordan are tweeners who would probably be better fits as OLB in a 3-4 same with Wake IMO. Odrick is a better fit as a 4-3 DT and I think Starks can play both schemes and Soliai was just coming into his own as a 3-4 NT when we made the switch. Really our front 7 is a mixture of different personnel that don't particularly work well for the 4-3...we still have more 3-4 personnel thanks to Ireland.
That's not to say that Wake and Vernon haven't done well rushing the passer but both have been inconsistent against the run but I can just imagine the fear in opposing QBs if we had both these guys standing up in a 3-4 rushing the QB.
We improved against the pass this year but we were much worse against the run and IMO that has to do more with the personnel in our front 7 than anything else. You don't go from 13th against the run to 24th against the run because the DC forgot how to coach.