check your cpu and gpu ussage while playing the game.
change the resolution down and up and note any changes in fps.
When I'm on max settings CPU usage sits around 50%. Sometimes it drops to 45 and spikes to 70.
As for my GPU, 80-99% activity according to AMD VISION Engine Control Center.
When I switch to lowest possible settings, CPU usage falls to 30-45%. GPU activity, 30-50%
I'm guessing its my GPU.