My experience has been similar - my 7900XTX chugs with this game. I am, however, running through wine/lutris (which I assume is the source of some of my performance woes).
You might try changing the RHI if you haven’t tried already. I get ~40 FPS in the base when using Vulkan (~90/327W, ~80% utilization). I get ~90 FPS in the base when using DX11 (~260/327W, ~84% utilization). I can’t really test DX12. Outside the base is better.
I really prefer how the image looks with Vulkan, but tweaking graphics settings only nets 1-2 FPS each (not enough for FPS parity) and the resulting image is worse than the best DX11 seems to be able to do.