I'd recommend running a GPU load monitor to make sure which part is bottlenecking you (like GPUz). In my case (R9 380 + i5 2500K) most situations are GPU-bound, meaning the CPU is not the limiting factor, however, in the large congestion areas (big active cities, hunts), the CPU load spikes and becomes the limiting factor. Since your GPU is much more powerful, but CPU is just a bit more, I'd say you're being limited by the CPU in the situations you mentioned.

Nevertheless, your fps is still pretty darn good and very, very playable.