Well you only *need* one core but the more you use, the faster they go. (Until they get completely bottlenecked by something else like your video card.)

125 means the operating system is reading your hard disk approximately twice a second to supply that copy of WoW with info that should be in RAM but isn't because there isn't enough RAM, or because of inefficient use of RAM, or because unnecessary programs are using RAM.

I would try to get those numbers to 0.