The WoW issue might also just be that the Linux scheduler is just scheduling all WoW threads on a single CPU. You could try to play with 'schedtool'.
Schedtool seem accept only 1-3 core configuration. Anyway i don't see any difference... but... today i've upgraded to karmic and I see an change: now on gnome-system-monitor I see on %cpu 70-90-104% cpu usage, but graphs show only 1 core used :?