Battle.net World of Warcraft want admin to update.

So this have happened a few times now. Im launching Bnet through Steam. There must be a way to fix this that dont require me to download ~130gb and reinstall it every time. Other games can be downloaded / updated just fine on Bnet it's just WoW that break. Im a fairly new user so i have no clue why this happen to me every few weeks after an install.