I found a way how to minimize the lag i was experiencing in crysis 3 and now the performance is good and consistent, gpu usage is ~90%
I reduced textures quality and manually reduced textures size pool which if i am not mistaken reduces the number of textures preloaded to vram. It would seem that this was a vram limitation however when i checked hdd usage it was much lower than before so i am not exactly sure what is the cause. Could be that game thinks that gpu has 2gb of vram instead of 1 because of crossfire and manages vram in a different way (mostly larger texture size pool). Anyways the things that helped me solve various crossfire issues were:
1. Clean driver install
2. Disable ulps (it reenables itself when you install/uninstall drivers)
3. Reduce texture quality and texture pool size in game.
Edit (just in case someone has same problems as me):
4. Change power profile in windows settings to performance. Apparently although neither of cpu cores were being loaded >60-70% it was still causing bottleneck. Some overclock i think helped a little bit too.Edited by cud0s - 7/8/13 at 6:58am