I have a gaming pc that is technically out of specs. On custom HIGH settings I don't crash. I've had one crash since owning the game which I got as a late birthday present and anticipated on launch day. I don't use shadows or settings that draw hard on the CPU. I have been told my pc will not run this game, yet I have 131 hours. I can have it running for 6-8 hours And while it isn't magnificent on my screen, it's still creating beautiful screenshots.
(Don't pay attention to speccy heat temp. Speccy doesn't get along with Windows 8.1)
My boyfriend can play on Ultra, but noticed CPU temps were extremely high when he did. He plays games like MWO and his modded Skyrim and Fallout doesn't even heat up the CPU like Planet Zoo does. So his answer was to get a sealed fluid cooling unit for his CPU and new fans for the case. Now his temps stay around 30c while playing, on Ultra. He still uses custom settings, lowered the shadows, the grass a notch, and it's fine. He played 5 hours his first day with no problems.
So I think these crashes are problems with people with maxed out settings and not paying attention to their computer heat.