I've seen people screaming about fps dropping to 15 or less during ICC fights....especially Marrow and Sindragosa.

From what I've seen, this is from the later version of MPR addon. After I disabled this addon, ICC fps is back up to 150fps.

If you are using MPR, disable it or get a different version. I hear 2.85 may work. I think I had 2.93B and it does not.

I run Grid, Healbot, recount, skada, tidy plates, omen, and Quartz with no issues until I enable MPR 2.93.