How much AA are you using? Maxed out AA should be around there.
Im running a 2560x1600 and 2x AA, that gives me 80 average, 50 minimum.
Have to say minimum is more important. I should scale back to give me 60 minimum. Every time there is a huge dust cloud in my face with lots of explosions my FPS drops. Any everything makes huge dust clouds. Its like the game got something to hide.
All the enginners use rockets, all the assault use the noob tube, and all the medics fire so many bullets they whip up huge dust clouds anyway.