Not to be a jerk or anything, but if you do a bit of digging, you'll notice that most of the D3 team are beginner-devs who have never shipped a AAA game before. Jay Wilson was the most senior member of the team (Duh, game director) and his credentials are not that strong at all (was a designer for CoH and WH40k), compared to other Blizzard dudes on different teams.
Not saying that's why D3 was as bad as it was, but being a big believer in the power of experience in all areas of life, one has to wonder. I personally think Jay W is a much better developer than most people think he is. I can't say the same for the rest of the D3 dev team. Except maybe Wyatt, who is clearly talented.