Hey, what's your GPU by curiousity? There is a large Probe Lights texture that might be causing some vram bandwidth issues.
The game seems to be more CPU-bound, though. I got terrible framerates (sub-20 fps on map 3) on an old system with a slow CPU but fast GPU (GTX 1070), and more playable framerates on a thin client with low-end Intel Graphics.
It also seemed to make no difference on an old gaming laptop with both Intel and NVidia GPU. I tried both, and got the same framerates.