I been getting slowdown in most of the Episode 3 levels, and maybe some of the later episode 2 levels. i'm not sure how to be more helpful with my description. i have been playing on Subjugator if that helps.
I would give more information but i kind of trained myself to ignore it, but then i thought -oh shit, i should probz report this just in case.
maybe i could go back and play again? Subjugator is hard tho
So i've intuitively learned of the map [mapname] console command to reload those maps that gave me trouble yesterday. i've been playing at the highest settings and the most i've experienced in terms of slowdown is slightly under 60fps. i was running through areas aggroing every enemy i could find and just dodging while i study the framerate (this was actually really fun for me) and it was all good!
So, i must have been running other shit in the background while playing the game that caused the slowdown. shutting down my computer and then booting it up again today must've fixed it.
Sorry for the false alarm