If you want to be up front about it, the the game cover should say "Diablo Online", not "Diablo 3 (with fine printed 'requires online connection')"
I strongly agree with this statement. If you are going fundamentally change a vision for a game, then name it aptly so. Much like Ultima went Ultima Online. The new SimCity should have also been called SimCity Online. These corporations know what there doing, especially nowadays when you can't even return games.
Don't sit there and take a game franchise that has strong roots with an SP Offline mode (a mode that got it off the ground with D1) and all of a sudden handicap it to online only, especially for a shitty reason of the RMAH... and then to turn around and release a console version that has an offline mode.