I had an issue when switching from AMD to Nvidia. I renamed my WTF folder just in case it was a configuration issue, and it fixed my problem. Just had to do some reconfiguring afterwards. I would start there. Since you aren't having issues in other high demanding games I doubt it's a hardware fault. But I could be very wrong.
If you haven't already, uninstall all AMD software and do a reinstall with the latest versions.
use driver sweeper or another driver cleaning program and remove all old gpu drivers from ati and nvidia. Then install the newest catalyst driver from the AMD website. Also if you have overclocked your card it might not be a stable OC and that could be causuing the issue
Hmm, i tried using driver sweeper and the result came up with a few NVIDIA driver (My GPU is AMD card tho).
I dont know why because i just DIY this system at 1 of the local PC shop and every part is brand new.
Anyway, pretty safe to say this is most likely the cause of the screen artifacts? Monitoring now and hopefully it will be fine.
If the issue is due to my GPU, will my other game, desktop screen have the artifacts too?
Well, wow is pretty much the only game i play now and this problem only started after i install on this new PC so not 100% sure if other game have this problem or not. Its pretty random when it occur so no real way to test it..lol
However, i did tried to follow some advice to run Fumark to test my GPU and i've found that after ~30min - 1hr, no issue whatsoever and the temp is constantly at 60+ Celsius Max.