We must define "bust" differently, because I don't consider a top ten player that turns out to be good but not great a bust. Rodgers might not end up one of the top 5 QBs in the game, but I think he'll definately be top 15... which is something we haven't had for quite some time.
Mediocre athlete? He's a better athlete than Manning or Rivers were last year. He's not going to rush for 400 yards, but he's got good feet in the pocket.
What exactly does "overly mechanical" mean? How does it keep him from being a better QB? What is the perfect level of mechanics and how does one become too mechanical? I believe Rodgers' mechanics are excellent and he has a very quick release. If you're complaining about his mechanics what did you think about Rivers or Carr when they came out?
Throws short too often is not suicide in the NFL. Throwing into double coverage, forcing throws that aren't there, and not taking advantage of what a defense is giving you is suicide. You have to throw short when you're throwing to 2 freshmen WRs that can't get open deep and have terrible hands. Last season Rodgers was throwing the ball up and down the field with great success and he's shown in the college all star challenge and his workouts that he's got a good arm and throws an accurate deep ball.