Diablo and Diablo II creative director Stieg Hedlund has admitted that the direction Blizzard took with Diablo III wasn't what he would have done.
When asked, "What did you think of Diablo III?", Hedlund stated, "It’s hard to separate personal feelings about something like that from how the game was perceived. I think the audience really didn’t react to it very well. A lot of the changes were things that they perceived as negative."
He added, "Personally, I was just so deeply involved in the creation of the world and how everything worked in it… The direction a lot of things went was not something that I felt was where I would have gone. But I don’t want to Monday-morning quarterback them. It’s a tough thing to follow up on, the success of Diablo and Diablo II, and not encroach on the territory of World of Warcraft."
Back in August 2012, Diablo II developer David Brevik gave his own criticism of Diablo III, and was promptly attacked by then-game director Jay Wilson, who dismissed on Facebook, "F--k that loser." Wilson was relieved of his duties for Diablo III this past January, and two months later he himself admitted the auction houses were a mistake.
Source: PC Gamer