I would say the largest % of people who bought the game don't give any sort of feedback, positive or negative, they buy the game, play it a litle, and never get involved enough to register their vote.
Of the people motivated to give an opinion, often they are the extremes, the extreme pro and extreme con.
I strongly believe that the complaints surrounding D3 are much more numerous and vocal than your average game, for a few reasons.
1. The game has many problems and is a major disappointment
2. People had ridiculously high expectations
Not a good 1/2 combo.