I'm not sure why they do that either, I do what I do in FPS, run and jump around the target. Most war skills only hit targets directly in front, so running and strafing do pay off.
The class i'm going for retail (WH) also gets damage bonus for attacking from behind on certain attacks, and also has some positional and reactionary attacks (i.e. disarms + damage if used after enemy parries).
I guess in these vids people haven't really played the classes and just record as they mouse click the taskbar buttons.
Thats good to know

Can't wait to try it out