It looks like the camera is in a fixed position and not actually attached to the character. You can see the barbarian get knocked around a bit at 1:10 and the camera doesn't move while the barb moves left and back.
As for how it's done, I'm not exactly sure. Probably an external program to manipulate the camera.
It looks good but then actually playing that way in a mode more then hard would be difficult. also you never move.