Danny's worst deals were of course to big men: Mark Blount, Jermaine O'neal, Raef. So in this regard he is no different than almost every GM in the league in terms of signing busts.
Scalabrine was a bad deal but that's not the kind of deal that gets you fired as a GM (see Lewis, Rashard; Smith, Otis).
As someone mentioned, we haven't had a shot to see Danny attempt to overpay anyone. This offseason was the first time we could have had cap space to sign a big FA.
I don't think Jeff Green will fall into the category of "overpaid" or "bad contract" unless he gets hurt or severely underperforms. If plays to his career average, he will be a typical NBA salary for his production.
Just don't see this. Al Harrington gives almost the exact position and production, but slightly better across the board, and people thought he was overpaid at 5 yrs 35 million. Or more years AND less money than Green. Marvin Williams is another one, almost exactly the same size, position, and slightly better production, and people make fun of his 5 yr 37 million dollar deal: again, less total money for more total years and signed when the CBA more favored players. This CBA was supposed to lessen player salaries, but Green gets more money for fewer years than extremely similar players previously received.
Edit-
I messed up. I was still thinking 4/40, not 4/36.
So the C's get 4 years of Green for basically the same price other teams got 5 years of Marvin or Harrington. That's not very good.
Also, another way to think about is that those other "bad" contracts were signed in the previous CBA, which was more favorable to players. In that system, the full midlevel, available to ALL teams (so there was more competitive bidding from teams, driving UP prices) was 5 years, with 8.5% raises, starting at 5.8 million, so ended up about 5 yr 35 million. In other words, Marvin and Harrington basically signed full MLE deals.
Green, however, signed for 4 yrs 36 million in the new CBA, in which the max MLE deal is only available to non-tax teams (driving bidding and competition DOWN), starts at 5 million per year, has smaller raises, and tops out at 4 years, 20-22 million or so. In other words, Harrinton and Marvin were worth Full MLEs in a system that favored players, while Green was given 175% of the full MLE (or 1.75 full MLEs) in a CBA that favors teams more than the old one. That's why it's an overpay.