Interesting discovery. I loaded Android OS Virtualbox guest using Genymotion
(Google Nexus 7 image with ARM translation installed) and tested the Google
Play version of Hearthstone. 

I am able to reproduce the same behaviour, hard locking my host (the machine
profiled above).  Black screens after an indeterminate amount of time running a
Standard match. My host machine is unresponsive to SSH access after most
trials, ... any suggestions for capturing diagnostics would be appreciated.