But the real question is on his status as a corner stone player. I consider him a very solid player and probably even a starter on a fair amount of teams, but not someone to overpay due to being too risky to lose him.
That's exactly it. If you're scared that someone will outbid you for him, let them! You need to set a price of what you think he is worth and clearly Colangelo overvalues Derozan as the "cornerstone" you mentioned. He isn't one. He's far from that. It's just a case of a GM overvaluing his own player. Same thing happened with the Bargnani extension.