Horrid FPS/performance....even on low

My specs are: e8400 4gb mem win7 64 bit radeon hd 4850 (2gb)

i tried enabling trilinear and shadows are off. no matter the resolution and graphics settings the game runs like crap, 20fps average in general and lots of slowdown.

Warzones are borderline unplayable

I can run skyrim on high, dota 2 on high N.P. but this game rapes my PC....anyone have any suggestions?

it seems everytime new textures load i also get a momentarily slowdown to single digit FPS