fps drop in select situation

i have a very decent rig and i run the game 100-200 fps without v sync on max settings but every time i get to the black magic spikes that the Templar destroys to get to John darr the fps drops to 15-30. in other cases i will get fps drops in co-op in not very intense combat situation.

i am currently using 2 amd radeon 6950s crossfire (also tested with single card v sync on and off) 16 gb ddr 3 ram, amd fx 6100 3.3 ghz 6 core cpu, sabertooth 990fx mobocomment if you are having the same or similar issues