Ill agree that WoW is a weird beast, I get anywhere from 50 to 800 FPS on my 9800GX2. Just keep tweaking with the settings til it suits you. Also what res are you playing at?
Also, ping can affect your performance.
Looks like you have a Q9300. Return the second GTX280 and get yourself a Q9650 or e8600. The Q9300 will bottleneck your GTX280s real bad. In fact, im willing to say that is probably your problem.
Depending on what game you are playing, the q9300 can have as little gaming power as a celeron e1200 or e2180/2200.
Hit me up when you figure this out, I am very interested in the fix.
the Q9300 has half the cache and clocks lower by far, and is usually not a good gaming performer. If you cant get the 9650 atleast get the 9550 or e8600. On non multithreaded games/apps your e8500/8600 will be your best bet, but a quad core is much more future proof.