I was just at an instance where Yandir Hard mode executes basically lowered the fps down to 15.
I have an RTX 2070 and an intel i7 H series processors (one of the newer ones).
My quality was at LOW.
PLEASE tone it down on the stupid effects. It was not just me, our group ended up wiping because it was so bad.
Also, there as a sound bug where you only hear the light attack audio.