A few things to keep in mind, while some of your heads are exploding:
1. Don't worry about LB depth. This is not Rod's 4-3. We will see very, very times, if at all, when we run out 3 conventional LBs. When we are in 4-3 in the new scheme, the 3rd LB will be SLB/DPR - think Smith, or Anae, Gregory when he comes back. In the 5-2 looks, you will likely have DLaw in a 2-pt stance with Smith or Anae on the other side, and then when we run nickel, we will have four DL and two LBs. So, it will be LVE, Smith, and Thomas - a very capable vet backup for both spots.
2. Fans and some sportswriters become enamored with "splash plays," but coaches watch the film on every practice rep, over, and over, and over. A LB that makes the occasional big splash play, but gets beat up between the tackles for the other 99% of the snaps, is no good to a team. I am not saying that I know he was poor, but we really don't know that he was outstanding, based on what a few beat writers wrote, especially this year, when only a few people could watch practices. Based on the fact that they waived him, he probably had some big holes in his game.
3. This was likely Fassel's call. I was wondering if he was in trouble when he mentioned that he was running with the 2s on special teams. As a backup LB, if you can't start on special teams, your life is short in the NFL.