I honestly thought offline D2 was a waste of time and couldn't care less that there's no SP mode. The closed nature of the B.Net realms were what kept me interested since they fostered a community, economy, etc.
As for defending their launch debacle...it doesn't bother me. Why? Because, in the grand scheme of things, if the game is good we'll all be playing it for years so who fucking cares if we can't get online on DAY 1 for a chunk of hours after waiting 11 years for a sequel? I sure don't, but then, I expected this and wasn't foolish enough to book a vacation day for the launch.
The people confusing this server-side game with always-online DRM similar to that of Assassin's Creed just have no idea what the hell they're talking about. It's not "always online single player mode DRM", it's a multiplayer game that you can choose to play by yourself. Don't have an internet connection? Sorry, D3 isn't for you. Servers are down? Them's the breaks, just like it was back during D2 for me.
I know people will kick D3's ass over some basic graphics, voice acting and so on, but it's Diablo. Diablo II wasn't a 180 degrees turn from Diablo I.
Also, I believe the game industry (Blizzard in this case) actually chose to do things like this because it works. Countless Call of Duty versions being only the same FPS in different environments, with some little changes here and here, still raked in lots of money. Diablo III will be a commercial success because it will be played for a long time, and it is still a Diablo game. You don't like it? Don't play it. You don't like being on the Internet all the time? I believe you already ARE on the Internet all the time, only for other reasons than playing the game. Get over it, plz.