When I first got the game I definitely remember the performance being a handful. Changing some graphic settings would cripple your FPS until you restarted the program. I also used to play via Proton on Manjaro and the performance was pretty bad, I had to turn settings down a lot. I haven't touched those settings in ages so no idea of those things still remain. I can say that I'm running a 1660 Super with a 12100F on Windows 11 at 1080p, and I limit my fps to 90 and it's solid. It's Ultra with a couple of things turned down. I'd say the campaign zones and monolith don't generally change in performance much, but the arena zones have way more mobs on screen at once and those give me frame drops sometimes. Haven't got there in this update yet but I suspect it'll be the same.

And yeah, monoliths are fun while you are still working on your build, but once you are getting close to maxing it and upgrades are potentially gonna take forever, the monolith content alone isn't enough to keep things interesting.