I stopped playing when I hit the wall in act 2 of the highest difficulty. I could plow through act 1 with ease but was getting shite loot then hit act 2 and got oneshot by ranged attacks from mobs offscreen. I Ground act 1 for a few days without a single useable upgrade and blizz's 'answer' was to go to the AH and buy upgrades. Diddnt bother playing much after that