Even though people like to think otherwise, the always-online DRM serves an actual purpose in D3 of keeping all your characters in sync and preventing hacked items at the same time.
It would have been fine if you were allowed to make a separate offline character, which had no relation with the online one. Its not having the online drm that is the main problem for people. Its not having an option of just playing the game without an online connection full time. If they still want online drm, have a check every time you start the game or every one hr or so. But not 24x7.