I do not see your “registry image”, it’s the same as the Dugi Installer image you’ve posted earlier.
    Can you at least make a system restore point and then try the .reg file.
    I have tested this on my laptop, on purposely preventing battle.net from running and removing the install path from the registry, rebooting then trying to update addon to get the same error.
    If you don’t want to run the .reg file then try using Battle.net app to Scan and Repair World of Warcraft installation, allow it to fully complete.
    I would like to do one thing at a time.