When I debuff multiple enemies with a high amount of debuffs/debuff-stacks (in my case armor shred, crit vulnerability, shock, and doom) my fps drop massively. It goes down from 144 capped to ~30 fps depending on the amount of enemies and debuffs.
To test this I went to the target dummies with a “Jelkhor’s Blast Knife” built that quickly puts a lot of debuffs on the enemies. The effect is barely noticeable on a single dummy but when I attack the big cluster of dummies the impact is massive. I watched the fps-graph and even when I stopped attacking the fps-graph only slowly stabilized until there were barely any/no debuffs left on the dummies.
During that the CPU-usage goes up a lot as long as there are multiple debuffs present. My GPU-usage goes down to the point where my GPU sometimes goes into idle-MHz (in echoes) for a very short time.
This is with a Ryzen 5 5600x and an AMD 6650 XT.
Edit: Video to demonstrate the issue (watch the debuffs and the fps graph).