Intel's single thread performance is absolutely demolishing when you compare it to an equal AMD processor. Because WoW only uses (I think it's 3 might be 2) threads, you can fit all of them on separate cores on an Intel processor and get much better performance. The flip side is that AMD has more cores, so when games start coming out to utilize them all, we *might* see the gap close.
A lot of the above is a little hyperbolic though at the top of the performance parts list tbh. I have an FX-6300 (work overruled gaming), and I still pull off stable 60 FPS in ultra 1280x1024, down to 40-50 in 25 man raids.