I find going to the NW side of the map to that forested area is the best to test your hardware.
Get the fps to 50 whilst looking around in the forest and you're garunteed a solid 60fps everywhere else.
The option for vegetation density, the max option KILLS all hardware, simply as it puts shadows on all grass blades. So knock that back one. AA is best set to FXAA. Leave all the advanced options off (such as extended shadow and render distance), max out all sliders for object fade in normal settings.
Shadows, set to soft, not softest.
Ummmm, everything else max at 1080p. That's what I had, got good fps, mostly 60fps with a few dips here and there.
I had a standard 780 (well, gigabyte Windforce OC edition), and it handled the game damn well. And as much as it pains me to say, the 980ti I've not got doesn't add much with a few options maxed out.