Lower your resolution to the lowest it can go and check your framerate, I bet it wont budge your framerate at all. You would be surprised to see how cpu limited that game is.
All of the other players running around casting random spells for no reason, mounting up, chatting etc is what lowers [cpu] fps at peak time in the cities.
Resolution helps it, but shadow quality is the main killer. Trust me, I've tested WoW with different setups over its 7 year span. I know what it needs to run at max settings no matter what you do. You can't throw old or cheap hardware at it and expect to run it smoothly at maxed settings.
