The goal of a defense has a couple of options:
1) your DL is a bunch of space occupiers. Which allows your LBs to roam and make all the tackles on the field. This is what we did last year. We did not count on our DLs to make many plays, they were there to tie up a couple of OLs each and keep the LBs clean
2) Your DL is expected to make plays so you count on your LBs to fill gaps left by the DL.
#2 was the way that I thought we would go this year. I thought we have a good enough DL and DBs to allow our LBs to just fill gaps and cover the in between stuff. However, we are actually playing a very BAD hybrid of the two. Our DL is attempting to make plays but our LBs are not filling any gaps. They are just in space and easily blocked by OLs. Also, as a LB, you have to make an OL WORK for a block. Be Shifty, avoid a direct one on one matchup. This play is exactly the opposite. We have both of our LBs attempt to take on blocks one on one and just get decimated by them. I very rarely see any NFL LBs take on an OL. If you have no other way to do it, you submarine them and, at the very least, make a pile in the hole