Punt returning was a problem with Leon Washington. It would make sense to draft a player like that if they were the best player available, but being able to return kicks should have little value at the top of the draft. There's guys like LeRoy Vann and AJ Jefferson that were elite return men in college that will more than likely be available after the fourth round.
Leon did look better the year before, when they weren't trying with him as much to be an every down back. Probably why Rex has said some of the things in the press that he has about him. Taking players higher because of ST is not rare though. Devin Hester didn't have a position but was still a second rounder. I thought the Jets should have drafted McElvin because of ST and he still went #11. Percy Harvin was also highly regarded because many thought he would be Hester-like on ST. Harvin improved the Vikes DRAMATICALLY and immediately on what has been a historically bad ST franchise. It's still 1/3 of the game and rookies can make a big impact. The Jet I always think of in this instance is Aaron Glenn.