Hey everyone.
TLDR:
If you play with fullscreen (windowed) and don’t want to have screen tearing you can enable vsync (keeping triple buffering enabled as well so you don’t lose frames when going below screen refresh rate) since Windows seems to be ignoring the option to disable fullscreen optimizations for WoW.
Long version:
I’ve been playing with fullscreen (windowed) and vsync off and for a while now I’ve been experiencing screen tearing. It worked fine in the past if I disabled fullscreen optimizations globally in Windows settings but after a while I started getting tearing. I thought it was something game-related that would eventually get fixed but that didn’t happen so I decided to look into it and found a great article from Microsoft explaining what those fullscreen optimizations really are and how they worked (for those interested, and since I can’t post links here, you can google for “demystifying fullscreen optimizations” and you’ll easily come across this DirectX dev blog post).
Basically, fullscreen optimizations bypass the WDM if you play fullscreen (windowed) so you won’t get the “free” vsync from it. The option to disable those optimizations globally in Windows settings is long gone now and it seems Windows ignores you when you try to disable it directly in WoW.exe (this seems to be the case for other games as well atm).
So I tried enabling vsync in game (keeping triple buffering enabled as well so I won’t lose frames when going below the screen refresh rate) and it worked! No more tearing 
I just decided to share this info in the case it might help someone else with the same issue and I strongly advise you to check the article I mentioned above if you want to learn more about how all these things work.
Cya around and best of luck!