I'm guessing more factors into the rankings than just how good the specific player was at UConn. It's probably some combination of the two. I doubt Kemba is a 95 overall if he wasn't a borderline all-star at the NBA level.
Still...however you're doing it, Caron being an 87 is baffling. He should be up there with Hamilton and Ray.
The Duncan/Kemba debate is probably unsolvable. One is obviously much better at basketball than the other, and that's certainly no slight to Kemba. Then again, they played in different eras, which complicates things...you could argue that taking everything into account (how good they were relative to everybody else in that particular season, the value of guard play in college basketball relative to other positions, leadership/charisma, context of how their respective teams fared the season after their departure, etc.), Kemba had a better, more accomplished season.