DD's contract was bad because there was no competition for him at the time. It's just bad business. Colangelo didn't let the market dictate his value. I really doubt anyone was throwing 8-9 million at DD this past offseason coming off an average year. I can't blame DD for taking the contract, he got way more than he'd earned up to this point and on top of that huge 4 year security.
So far, he's played up to the contract for the most part having improved in nearly every area. Still, he could likely improve more. It's nowhere near the worst contract we have though!
BC is like that guy at an auction that thinks "I'm gonna start high and blow everyone else out of the water" when it comes to contracts and I don't think that's the best approach to take.