https://bugs.winehq.org/show_bug.cgi?id=39261
--- Comment #3 from Johannes Dewender wine@JonnyJD.net --- The workaround provided by neotrax doesn't work for Hearthstone, since that game needs the launcher to login. Starting "Hearthstone.exe" does start the launcher after the hearthstone windows is shown briefly. However, starting like that seems to work quite often. I could only reproduce the problem once for Hearthstone (without changing things).
The issue seems to be the order/time when the battle net agent is started (again? similar to https://bugs.winehq.org/show_bug.cgi?id=36216 ?). I made the launcher work for Diablo 3 when launching "Diablo III Launcher.exe" getting the error, closing it and then launching again (when Agent.exe is still running).
Although I mentioned that similar bug, this is hopefully not the exact same problem since that bug includes a fix in 1.7.42 (I am running 1.7.49) ATM.