The other thing is, and I've said this quite a bit before:
JJ Watt and Justin Smith play in one-gap 3-4 schemes...the Steelers and the Patriots use two-gap 3-4 schemes...
Who were great Patriots D-Linemen? Richard Seymour (#6 overall) and Vince Wilfork (#21 overall)...
Here is an interesting article on the comparison of the 4-3 vs the 3-4 on rushing the passer.
3-4 vs 4-3 comparison
When the Steelers were the only one or one of the few teams that did the 3-4 they had better pickings at nose tackles of need or linemen/linebackers of need at the time. So many teams now run the 3-4 we no longer have the resources that are needed. Everyone wants the giant nose tackle and the gifted linebackers that fit the scheme.
Time to trade back to the 4-3 and many teams in my opinion now have a more difficult time adjusting to the 4-3.
I know, as long as Lebeau is around the 3-4 will be around. Things go in cycles and I believe the cycle of the 3-4 will soon wear itself out do to lack of players to fill the position.
The DL/pass rush struggles have gone hand-in-hand with the decline of Casey Hampton. NT is the key. Get a guy in there that commands a double team on every snap, and somewhere along the line you'll have either a DE or LB that is one-on-one or better, uncovered. If Cam Heyward plays up to his physical skills, then he'll also draw double blocking. That opens up everything.
Steelers DL at their prime had Hampton taking up 2 blockers, Smith taking up 2 blockers & Keisel taking 1 OT. No wonder the LB's were so dominant.
NT is the key to the 3-4, always has been.