Although it’s not quite the offline mode that many were hoping for, the ability to appear offline so that you don’t get harassed while trying to shank as many innocent demons of Hell as possible is something that has long been missing from Diablo III.
Patch 1.0.5 will be remedying that, allowing you to appear offline to all of your friends regardless of whether they know you through RealID, BattleTag, or even just in-game as character friends. “The ‘Appear Offline’ status option will be added to World of Warcraft, StarCraft II, and Diablo III separately in future updates for each game,” writes the official announcement.
“For Diablo III, we expect to add the feature in a patch after 1.0.5. For World of Warcraft and StarCraft II, we expect to add the option sometime after the release of each game’s upcoming expansion.”