You know, as much talk as we hear about how Dez is one of the hardest working, hardest practicing players on the team, why hasn't his route running improved? Also, why doesn't Linnehan move him around?
The knock on Dez' route running has been overblown. He took a couple of years early on to get it down. But they do move him around the formation and he does run a variety of routes.
His real issue early on was struggling to make the right adjustments to routes based off of what the defense would do, and he and Tony would be on the wrong page as a result. Tony covered for him, but it was an issue. But even that he got sorted out by his 4th year or so in the league.
Dez is fast, but doesn't have elite speed, and good cover CBs can limit him if their good enough to stop him from high-pointing the ball. You can't really play him too physically because that's part of his game, too, so the refs let it go. So guys like Xavier Rhodes and Jenkins and Norman can more or less play him to a tie. That's fine. If you don't have a guy like that, you have to roll coverage to him. If you do, we're checked on that front, you take your chances, and you attack elsewhere. He's still a valuable piece of the puzzle, and he's capable of beating good coverage now and then, too, so you can live with it.
He's not elite, but that's ok. He's very good. And he's about to have a very good year if he stays healthy.