I'm OCD about my rig, so it's always a clean display driver install (DDU+cache cleanup etc.). I haven't tried disabling SLI because it makes my blood boil having £500 worth of kit sitting doing nothing (I bought both GTX 980 as nVidia reference cards the weekend they were launched, so paid early-adopter penalty prices).
Setting everything on high/ultra, but setting grass to '0' still works. I did read disabling SLI also worked, but it's a pain in the furry hoop to toggle SLI on and off on a multi-monitor setup just for one game. I only recently came back to SWTOR after 5 years, and I am enjoying it. But this bug is seriously irritating.