This sounds very similar to our Flickering Issue thread here. Our team is aware of the issue and working on a resolution. Hopefully, it’ll be soon, but at the moment there is no ETA on when this will be fixed.
There have been some odd fixes with textures and gamma settings. Let’s try playing around with these settings. Right click on the desktop and go to Nvidia Control Panel. Under Manage 3D Settings, turn OFF the Antialiasing - Gamma Correction.
If it continues, could you try turning off Projected Textures in the WoW client? Press ESC while in WoW, go to System > Graphics and set Projected Textures to Disabled.