Indeed the investigation into the cause of this is still ongoing and there is no current ETA for a fix.
Just to re-iterate the currently available workaround:
- Uninstall and reinstall WoW
- In the Battle.net app Settings -> Game Install/Update -> Turn off download future patch data under Automatic Updates, by changing the selection to “Apply latest updates for recently played games”
Additionally, I couldn’t say if any future fix will retroactively heal up existing installations, so if anyone is still holding out on re-installing, now might be a good time to do that or make arrangements for it in case data transfer caps need to be considered.