Install pretty much same as it says for Dark Souls 3, but aim it at WoW.exe instead
It makes WoW look pretty depressing and loses most of its color. But I like the look. Keep in mind, HDR can be toggled with insert key and in the day it might be way too bright with it on. I'll have to wait till tomorrow to see how bright it'll look, but looking at the blood elf screen the background is far too bright. Toggling HDR off fixes that though, so HDR will look good in some situations and not in others. However all screenshots are with HDR on.
My Skyrim, Fallout 4, Starbound and WoW + other game mods at MODDB: