Hi,
I have been monitoring my system the last days during the game using perfmon (for CPU, RAM and HDD) and gpu-z (for GPU and VRAM). The results show, that the GPU and the VRAM are the limiting factor. Both are at 100% during the game, whereas the CPU never reaches that limit. Normal RAM never drops below ~1GB and the HDDs are almost at 90% idle time.
So I think it's time to think about an GPU upgrade. The situation might be less worse with the upcoming patches, but I wouldn't count too much on that - in my special case, the GPU seems to be totally outdated

which is ok, because I've paid only a few bucks for it