OP - I was having this exact same issue on FF, Overwatch, and other games. PC would hard crash, all fans would kick into overdrive.
I replaced my PSU and I haven't had any PC crashes since. I am now having issues where FFXIV just randomly disappears with no error or anything, but my entire system doesn't crash...
You could be having a power supply issue like I was..OR..
If you're running discord, try disabling hardware acceleration in the options (there two separate places) - this is causing crashes for some people.