It's really hard to attribute a certain level of credit to a G.M. Obviously there is more credit/blame to go there than anywhere else in the organization but it's still more complex than usually presented. Ben, for all his faults built up a good farm, and even Theos guys came into the system when he was assistant G.M. what level of influence did he have in those decisions?
His biggest folly, whether you want to blame him or the organization has a whole has been drafting and developing pitching. I'm not the biggest DD guy but one thing he has done is use the assets within this organization to build up the rotation and the bullpen. Yes, we have zero depth now, but that's because we have Sale, Pomeranz, Kimbrell, Smith etc. The farm is important but sometimes the point of having assets is to trade them for what you need.
I have no idea what DD's plan is, or to what level he has a plan this year but if you step back and look at this team as a whole it's blatantly obvious what he's done. He took a team that was rich in talent on one side of the ball and kept the young cost controlled MLB ready players, and he moved other assets to build up the other side of the ball. The results have been two straight division wins, and it looks like this team should be just as strong for at least another 2-3 years.