Here is a quick fix for the blank/non-responsive screen in when going full screen in Pillars of Eternity on OS X (El Capitan). Note that you will have to do this before you run the game each time as it will reset the settings with bad ones each launch.
Project Licenses
These works by Jeremy Pyne are licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License