What I am reading between the lines about how he takes a step forward and a step back and seeing him make a couple plays when he does get snaps is that he does a poor job in the class room. How that manifests exactly I don't know but it is clear they do not trust Cox.
LVE has no catchup speed but he does have decent quickness and now he is over his neck surgery he is taking on blocks again like a champ. He is what he is and is a fine LB.
Clark is the key. If he can step up and learn his keys and get a little bit of coverage instincts and he could be a real difference maker. He is undoubtedly strong, fast, quick, and willing.
After that it is depth because our base is a big nickel. Overshown was a need pick but we have him. Harper and Cox round out the roster. It's kind of thin but one of those three cannot be much worse than we got from LB2 last season.
Compare that with the Eagles who lost two starting LB to FA and replaced them with a big bowl of nothing.