That's odd - it runs smooth as silk for me at 1080p on max (rig in sig). I know the latest patch added improved room and mob culling logic to address some performance issues on the larger levels (Update 3 I think it was).
I can never be free, because the shackles I wear can't be touched or be seen.
i9-9900k, MSI MPG-Z390 Gaming Pro Carbon, 32GB DDR4 @ 3000, eVGA GTX 1080 DT, Samsung 970 EVO Plus nVME 1TB