Not true - WOW has been universal binary for quite a while.
The internal Graphics card is the culprit if you have at least 1GB of ram. The options most affecting it are full-screen glow and 2 other I don't recall - but try it at screen-native res, but with all options off, and work your way up.
If it stays in a 8frame or so even in 'open' areas, I might re-install, or re-apply the OS update...
cheers,
dan