With such hardware it should “just work” so with some investigation it could get solved. Lack of native fullscreen limits SLI and Crossfire usability but those technologies are pretty much dead nowadays. With one GPU you should not get such results.
To troubleshoot this problem:
- Run latencymon - check if the system will report problems there when the game has performance spikes (if so it could indicate a driver or OS problem, to be retested on clean system install)
- Run MS Process Explorer - check if anything in the wow.exe resource usage is out of the ordinary (slow network tracerout to server it’s talking to, I/O on the SSD, CPU/GPU/thermals/power
- Similarly HWinfo can be used to log every sensor so they can be checked after - if any of them is out of bounds and could indicate the source of the issue.
- If other games work fine the the overall system should be fine but you can run userbenchamark and check percentile scores of your component. Very low percentile can indicate problem. You can also try running the test during performance problems in WoW to see which percentile gets the biggest hit.
- Are you using any addons? There could be a conflict or a bug somewhere there - worth testing out.