The 'fps lock' you are talking about is what I mentioned earlier, called Vsync - all it does it synchronise your framerate with the refresh rate of your monitor to make it as smooth as possible.
Yeah, I do think WoW is more demanding than people think at higher settings. Your 8800GT is a fairly powerful card, but that is a high resolution you are playing with, and I don't think the WoW engine really handles lots of players on screen at once that well.
I'm sure a newer graphics card would solve your problem, but to be honest, 30fps minimum is definitely playable. Hell, I've got friends who play the game on 5 year old laptops - 9fps max.