According to the Youtube description, the video took over a year to make, using MotionBuilder, 3ds Max and Wowmodelviewer to pull it all together. Let's be clear, here: Creating new animations is not as easy a task as you'd think. This tiny, 4 minute video took well over a year to create. However, I still find it pretty astonishing that the old character models can still be taught new tricks. And I still hold out hope that one day, we'll see different dances for all of the races in the game.
Until then, we can go ahead and watch Oveoflod's video and wonder about the possibilities of what could be done, given enough time.