There's the Horde's Battle for Lordaeron stage where they can elect to fight people or save people. There are several quests (mostly world quests) where filling the % progress bar can be done by interacting with objects instead of fighting mobs. Numerous quests require no violence at all, but it's not in lieu of a non-violent route (gather these things, deliver this item, etc.). Ultimately of course the decisions don't change the outcome, because the state of the world doesn't generally differ player to player (aside from things like phasing where one person is simply behind progress compared to another).