I have been focusing on him a lot this year. This is what I have noticed.
1. He takes just about every play off. I never see him sprinting to the ball.
2. He lets himself get absorbed on blocks. He can't shed a block to save his life. In fact, it appears he walks into blocks just to get occupied and sit there.
3. Because he is never sprinting to the ball, he never makes a downhill tackle.
4. He is completely lost in man or zone coverage responsibilities.
I would comment on his angles, but honestly, I rarely see him pursuing the ball carrier. If they don't run right into him, he is nowhere to be found. He is a failure because of lack of effort.
I agree that it's not a scheme issue per se; although, I do think some of what appears to be laziness is over-thinking that leads to slow reactions.
He does seem to lack intensity and focus at times. He's some had games where he was reasonably good.
Analyzing a LB taking on blocks is tricky. If he sheds a block, that means that he committed to 1 side of the blocker and can take himself out of the play. He is required to "stack" the blocker until the runner commits to a side and then "shed" the blocker.
He would be ok if they were always in man coverage, but he appears to forget which coverage they are playing at times. He definitely played man when everybody else was playing zone on the play that was highlighted by the announcers.
I'm guessing that he is a slow learner. He was on an evening radio show earlier this season. I think it was the Brad Sham show. He didn't "sound" like the brightest bulb and he said that Sean Lee is constantly quizzing him about the defense even when they are in social settings or at each others house otherwise relaxing.