So I'm having the same issue as another guy that posted here recently. CPU bottlenecked for no reason, ever since the new season 2 update.
I uninstalled and reinstalled now I'm getting 99% cpu bottleneck. Used to get 220 fps fine and pretty sure it was the other way around like 90% gpu bottleneck. I checked almost everything.
Updated BIOS, chipset, changed bunch of settings, reset, blah blah, I even overclocked my CPU to 4.55ghz when I was getting 220 fps before with no overclock because it wasn't my cpu that was bottlenecking.
I checked hwinfo64, during benchmark, CPU never even hit 20% max usage, nor did temps go over 70c.
It seems like its the game itself, other games I play have no issue. What else could it be?