i have an amd phenom II x6 (1055T) and it runs fine. my FPS may drop to 30 in dalaran (my main toon) on ultra settings. Of course I have an SSD and my video card is an ATI 4890 1GB.

the CPU isn't taxed too much for me.. most I see on any core is 25% utilization. (but they are usually all at around 15% with spikes to 25%)

btw I have 8GB RAM.