I too have a 1600x and a h100i V2 with the same problem.
Now i have everything at stock with an idle temp of 35-45, but when i play an old game like MW2 it does sometimes go ut to 70+ degrees.
And i cant remember that this was a problem when i first built the system back in 2017. I used to play pubg back then with an OC of 3.9ghz@1.325V with temps around 65c.
It might be that the IHS is uneven which makes the temps to raise. And if thats the case, the only thing i can think of is to die-lap the CPU.
Not sure tho..