Not sure if its just me but, On days 1-5 I normally would get 40-60 FPS but as soon as the boss fight comes about I get about 8-10FPS.
Computer Specs are
2x Xeon Platinum 8176 @2.1GHz it does boost to 3.8GHz on a couple of cores
AMD RX 580 8GB
128GB DDR4 ECC
I do also run the game with Linux under Proton.
For the record the games not to blame its just the slow clock speed. Sorry
Update. SInce Iām on Linux and not everything is obvious had to use a external utility to do this since I needed to change the fan curve on a GPU.
Turns out the default power governor for my setup is Powersave which means the CPUs average 1GHz when its not under a heavy load. I change the governor to Performance and it shows the average is 3.5GHz on the active cores I assume. My performance in the boss fight is I think a perfect 60fps now.