Have you tried toning down any CPU overclocks? My game use to crash because I had an unstable overclock.
A month ago my 9900k was at 5ghz and I was having poor performance and crashes mid raid. The funny thing is my other games didn't seem to be affected. I used many crash fix guides on Google and none of them seemed to work.
I just defaulted my BIOS and the game ran so much better. No more crashes!
I've since overclocked to 5ghz again and everything is holding up great