My machine is very similar, and it eats wows for dinner, I've ran 10 on it and it was just as smooth as 5. You've def got some core issues, as did I. Assign each wow to 2, I can't remember if cores started at 0 being your first core, but essentially it was 2 cores for each wow, and 1o cores total. The only time(s) I ever had lag, and low fps was due to my power supply going, and another from a virus. Fiddle around with the core affinities, and start ur wows at the lowest grapphics and scale up from there. It could be one graphic setting messing things up. Shadows was something I tuned down a lot.