I played the game for something like 6 hours over the weekend on DX11 with VSync enabled. No crashes. As far as workarounds go this will do for now, but my eyes are noticing the differences with screen tearing and such. I'd like to have it back, but I'm not going to push the issue further.
For comparison, I did a few more test. Vsync disabled and Gsync enabled for all tests.
Minecraft, 140 FPS at about 78C. No crashes, tested it for an hour.
Mass Effect 1, DX8/9, 100+ FPS at about 80C. No crashes.
Alien Isolation: DX11, 62 FPS at about 83C. No crashes
Kerbal Space Program, 64 bit, also Unity engine, 140 FPS (in space, using a small craft) and assumably DX9. No crashes.
Kerbal Space Program, 32 bit, also Unity engine, 140 FPS (in space, using a small craft) and assumably DX9. No crashes.
The Long Dark + NVidia stress test tool, 91C, FPS 25-30, DX11. No crashes for two hours.
Conclusion, the problem is currently specific to The Long Dark and very high framerates. Even forcibly overheating the GPU doesn't force a crash with any of these games. Unity may be a factor, but I don't own enough Unity engine games to tell for sure. KSP works fine in 64 and 32 bit, but I don't think it uses DX11. I don't own any other Unity games that run DX11, so I am unable to test that further.
I pinged my contact at NVidia. I was one of the first people to test a GSync screen, they have always been interested my in feedback as a result. They're usually very interested in learning about issues with relatively new tech, but It's been a while since we spoke and GSync isn't the latest of the latest anymore. High frequency monitors however are very commonplace, even if there's no GSync technology in them. If anyone would know if this is a common issue with Unity games, it would be NVidia.
I don't know when or if I'll hear back from him though, you might want to do a little inquiring on your own.