On my system the game is completely CPU bound.
Seems the game can only utilize one core fully and then some on the extra cores.
Turning off v-sync and cap stops my FPS around 90. GPU load is less than 60%.
CPU load is then around 40-50% (one core maxed, others in partial use)
I have a GTX 780 GHz Edition (overclocked to 1142MHz, stock 780 is 863/900 Mhz)
And a i5-2500K @ 4.3GHz.
No reason to run game above 60FPS tho, since I have 60hz monitors.