https://bugs.winehq.org/show_bug.cgi?id=53826
--- Comment #2 from Adrian Demarais adwinebug@adrn.no-spam-allowed.com --- Turns out that replacing the current battle.net plugin (/home/whoever/.wine/drive_c/Program Files (x86)/Battle.net/Battle.net.13763/platforms/qwindows.dll
with a qwindows.dll from a previous battle.net folder will allow an already-installed battle.net to run.
I expect anyone attempting a first install would be out of luck, having no previous qwindows.dll to fall back on.