Okay, not to get too into the whole 'WoW should steal every Diablo III mechanic and idea' bandwagon, but have you played a timed event in Diablo III? They're similar to the treasure room from Throne of Thunder, but they're randomized so you sometimes get a random dungeon to explore on a timer, sometimes you have to kill endless waves of stuff to get an extra treasure chest, some times it's a special monster trapped in an urn but it's always awesome. It's fun when you get it done, and even when you don't get it done it's awesome just because you immediately start planning out how to do it better. I actually have specific talent choices just for the timed events.
It's a mechanic I absolutely love, and I want to see it in WoW so bad. We've had escort quests before, and a few world events, but this particular mechanic I think is just awesome. So please please please World of Warcraft masters, steal from your own company.