Ofcourse it's the memory leak, you can have a monster machine and it still cause troubles, i don't have monster but it's still a solid PC to play, i have a really smooth gameplay at the beginning, but the more i play the worse game works. In my case it's starting around 2-3 hours of game running, then when i turn off game it takes around 5 minutes to go to desktop, PC needs restart because it's not usable, which also takes time, around 10 minutes.
In short, it takes a solid 15 mintues to exit the game and restart computer.
I have i7 6700k 4,5 GHz 16GB Ram and GTX 1070...
I honestly think, this and crashes that people experience should be priority, and i will gladly await for some hotfix. I ahve like one crash for the 5 hour of playing, not bad, but from what i read, some people have more and some can't even launch the game.