Well Vsync only works when the game is full screen
This is not correct. Vsync does work in fullscreen windowed, as I play in full screen windowed.
I use adaptive vsync in the nvidia control panel. The ingame vsync option ONLY works while fullscreen, to enable vsync you must do so in the nvidia control panel. Make a program profile for WoW in your nvidia control panel, or make a global option with adaptive vsync / vsync on. This will enable vsync even in fullscreen windowed.
Fullscreen mode for WoW sucks because the screen blacks out for 3-4 seconds while switching between the desktop and the game. With fullscreen windowed, it is instantaneous - and you can also view your desktop at the same time with multi monitor (on a different screen). Since skype, streaming and mumble are pretty integral for many wow players (including myself), fullscreen windowed is the best mode to play it with. I can't imagine using fullscreen for WoW, ever.