You couldn't have been following recruiting very much at the time if you considered Richards a sleeper at the time of his recruitment. He was just as touted as Stephon Hannah or Blake Young out of JUCO. NC State wanted him bad. Granted, the other main players were Auburn and Butler, but its not uncommon for Top 20 JUCO players to list a variety of schools. Richards wasn't a "can't miss" JUCO recruit, there are only a couple of those a year, but he was certainly he was more than a sleeper. There is no doubt that Richards didn't even come close to living up to his billing out of JUCO. If I remember right, BP was very high on Richards coming out of JUCO.
The only other guys that could really be considered sleepers on your list are DaBarrosa and Yearby. By that I mean that at least one recruiting service reportedly said that they were guys people were missing on. The rest of those guys would be more project recruits than sleepers.