People, Vernon is not a particularly agile athlete. He just isn't. He never will be. It doesn't mean he's useless, or not gifted in other ways, but he's simply not a dextrous player. Wishing or asking him to be one is, to be blunt, a waste of time.
Vernon's balance and body awareness have never been particularly great. He also runs fast, but is slightly out of control at his top speeds. He's quick to explode forward but doesn't change direction very well. His coaches and people who knew him at Maryland were open about this. More to the point, all this is obvious to anyone who watches him play.
Basically, Vernon is a weight room freak who has willed himself through extremely hard work into being a very good player.
Balance and body control are at least as important to breaking tackles as power. Vernon will never be a massive tackle breaker in the NFL, no matter what his height/weight/speed stats read. Asking Vernon to "run lower to the ground" like Frank Gore does is like asking Gore to run a 4.4 like Vernon does - it's just not the type of athlete they are.