Nothing wrong with Nvidia in WoW, except two 780 Ti's in a 10 year old dual core MMO.
WoW bottlenecked on my 1090T @ 4.5GHz with a single 900 MHz 470 in high pop areas.
It shat all over two 950MHz 470s in SLI with a 5.3GHz i5-2500k. If you go away from people your FPS will shoot past 170+ FPS, you go into Stormwind for instance and welcome to 40-50 fps when there are a lot of people around.
Problem is insanely powerful GPU setup, coupled with trivial to run graphics, within a thread limited title.