As others said, this is not a problem easy to replicate. I had crashes very close together and then nothing for a week. I'm 99.9% certain that this is a software issue because a) it never happened before, and b) it never happened again after I downgraded to 10.11.3.Presumably though, running 10.11.4, i am using the same driver as everyone else?
(And thus, i should be able to replicate the problem...)
edit:
Oh, i never use in clamshell mode. 99.999% of my use is internal screen, trackpad and keyboard only.
Maybe there's something in that? For those having crashes, are you swapping between external display and internal display without rebooting? Not apple hardware, but the intel video on my Surface Pro 4 totally loses the plot and has display driver crashes on a reasonably regular basis, and I dock/undock that on a reasonably regular basis without rebooting it.
I know - windows driver vs. OS X driver, but as I understand it intel probably provide most of the driver reference code, so wouldn't surprise me if there's some common video mode switching bug in there somewhere... i.e., switching between internal and external display may trigger some dodgy code in there which doesn't reset things properly when switching?
Edit: better than check with year your Mac is or what OS came installed, is to check what CPU is included. The problem seems to be very common on Broadwell architecture CPUs.