It's not about whether the game is fixed or not, it's about the business's management decisions. Lots of people won't buy EA games, for example, regardless of the quality of the title itself, because of the business's conduct in the past. The simple act of shipping a fixed game doesn't equate to the necessary cultural shift from the developer that would merit returning to the game. It's not as if they've gotten rid of Bobby Kotick as the head of Activision Blizzard, or said they'd commit to a long-term fan-driven model across their titles. It's essentially a boycott.
On top of that, we're talking about rewarding them with more money for what is, at its heart, an old product with some refreshes. Expansion packs and other forms of non-free DLC are only really effective at drawing in consumers when the base product has something the player wants to continue. Many people (myself included) got sick of the repetitive, imbalanced structure of the game a year and a half ago, when it first came out, and we have no desire to relive those memories or anything tightly associated with them. D3 had a breathtakingly uncompelling story; the adventure RPG equivalent of a cookie-cutter save-the-cat blockbuster, only without any character development whatsoever. (Unless you can think of a game with a lamer ending cutscene?) Even without the auction house, crazy elite monsters, terrible loot rates, failure to learn from competitors and clones like the Torchlight and Dungeon Siege series, the total lack of character personalization, and the extensive balance issues, I think the exploitative, sequelitis-infested anti-plot would be enough to keep people away from any continuation of the franchise.