Turn down view distance, item textures, and shadows. Leave particle effects, gloud cluttering, aoe, that kind of stuff up. You'll drastically imrpove your frame rate and maintain all of the visuals that are needed to see. (Does it matter if your armor looks like crap while your raiding or that you can see Westfall from EPL? Not really.)
Anyways, I do not have any of the mentioned problems running on an i7-950 w/ nvidia gtx460 @ 800Mhz which is far less powerful than mentioned. Problems are either overheating or something is bottlenecking because of visual settings. Big offenders for bottlenecking are shadows and view distance. The further your view distance is set, the more (exponentially) it tasks your processor and video card.