re: LSU defense, would LSU be better running a different defense?

Because Chavis recruited tp many speed rushers that are not strong enough to get by 325lb tackles

I think the problem with the DEs, as well as the DTs sack numbers, pressures, hurries etc. the last two years is simply Chavis didn't feel(probably correct)that LSU didn't have the depth with quality players than he did in the past on the DL. In 09 thru 12, he had five and often six players at both positions. The 3rd and 4th guy had almost as many snaps as the the starters and 5th and even 6th guy typically played two or three series against every really good opponent with very limited drop off. This didn't happen in 2013 and 2014.

Sadly the performance of the back ups hasn't been there when they played despite having about the same recruiting stars.This made Chavis play the starters more than before.

As every fan should know, it takes more energy to play the DL than the OL which is why at the NFL level and big time college football the DL always has some sort of rotation and OL rarely does.