Macbook Pro intermittently unresponsive/dark screen after waking from sleep
You may want to rule out a graphics card issue, which impacted select 2011-2013 MBPs:

http://www.apple.com/support/macbookpro-videoissues/

And if you haven't done so already, run Apple Hardware Diagnostics:

https://www.lifewire.com/use-apple-hardware-test-over-internet-to-diagnose-problems-2259973