Noel is a rotation level player on one of the best teams in basketball. As a 6th pick that is about what you get on average. For example, his WS/48 are .107 which is good enough for 15th all time among 6th picks. his total win shares currently has him at 36th of 72 all time 6th picks. He will move up another 4 or 5 spots this season if he continues at his current pace. He is 10th among 6th picks in rebounds per game and is 34th in points per game.
In other words, I have a hard time calling Noel a bust. He is about what you normally get from the 6th pick. I mean these are the 6th picks starting with the most recent going back to our very own Antoine Walker.
Bamba, Isaac, Hield, Cauley-Stein, Smart, Noel, Lillard, Vesely, Udoh, Flynn, Gallinari, Jianlian, Roy, Webster, Childress, Kaman, Wagner, Battier, DeMarr Johnson, Szczerbiak, Traylor, Mercer, Walker
This is not exactly a whose who of greatness. Sure you have guys like Lillard in there, but Noel, even right now might be in the top half of that list, with plenty of time to move up it.