Most of the comments here summed it up pretty good for both sides. What the people saying D1/2 had offline why can't D3 have it. Is because D3 wasn't designed for offline or single player. It was designed for a coop arpg loot hunt. Yes the drop rates were very wrong, yes the AH love or hate changed the way people thought about the game. But D1/2 were designed as a single player exp first with multiplayer added. D3 was the other way around. Games change, if you like it or not that's just a fact and you have to live with it(read as buy or not buy the game).
Don't compare simcity because there a difference in a game were you make your own town and were you run around in a group killing things. IF simcity did something like you and your online friends designed the town together, then maybe... but it's not. The online is just so you can look at each other towns and try to do trading. The offline mode for D3 doesn't bother me, it's all the bitching and whining that people are still doing about it and not even realizing that there's a difference. Oh yea consoles have an offline mode, but they had to totally revamp majors systems in the game and still want you playing 2-4 player coop instead of single player during it.
Funny thing is D3 did GREAT with having online only.
Munching On: Archeage, SAO Vita, Tales of Xallia 1/2.