If I don't use processor affinity, then 2 of the cores will be nearly pegged and the other 2 don't seem to get used much. And the fps in each window seems "normal" .. 20-30 fps
WoW only supports up to 2 cores at the moment, so this is correct.

Not sure why the FPS drops when you manually assign processor affinity, but its possible that its not suppoorted correctly via the applications (keyclone or wowmaximiser?)...

Cheers,
Stealthy