So whether it’s single or multiplayer depends on a difficulty factor?
Quake 3 is a multiplayer game. You can play it by yourself, against bots, but that’s not really the design intent. I did that quite a lot, so I can understand the Diablo fans that want to play Diablo by themselves, even though I think that’s kind of crazy because it’s so much more fun with friends.
If, back in the day, Quake 3 was the exact same game (multiplayer with optional bots) but iD software had integrated a friends list, with drop-in drop-out to their games, and cross-game chat with other iD software games, and the ability to look up your player stats and achievements and stuff on the web and build on those from any computer you have Quake 3 installed on, and to install Quake 3 on as many PCs as you feel like (because hey, you’re logging in), and so on and so forth… would it be okay if they required a persistent internet connection? Would we say “that’s just DRM” or would we say “they made an online-only multiplayer game, but they’re not going to stop me from logging in and playing it by myself.”
How about Quake Live? It’s just Quake 3, really. The same game we played offline (if we wanted) years ago. But it’s played in a browser and requires a persistent connection. Is that just DRM? Or is an online-only multiplayer game, that you can choose to play by yourself?
Functionally, Diablo 3 works like WoW, from all appearances. You have a dumb client. All your characters, and every shred of gold it picks up and every skill it earns and every monster it kills and so on…all handled on the server. Your client software is there to paint pretty pictures and make neat sounds and stuff.
This is a lot different than, say, Assassin’s Creed. It had “cloud saves” in that the game played entirely on your PC, the game was saved to your PC, and then that saved game was copied up to a cloud server.
I fully understand the complaint of “they didn’t make a single-player offline mode!” but I think that is quite distinct from saying “they just made the same game with always-connected DRM!”