on what kind of drive do you have FF installed? (HD/SSD) usually when you have GPU/CPU intesive games installed on a regular SATA drive you get a bit of a hardware lagg because of the read/write operations, specially when moving, because of the constant loading of mapdata
I myself have tera installed on SSD and am running it without problems, no stuttering whatsoever
Sli is fully supported btw :3 i'm running 2 690's (quadSLI)

My Specs:

Intel I7-3960x Stock speeds
Asus Rampage IV Extreme with default settings
32Gb 1600 cl9-9-9-24 X.M.P
Dual GTX690 (326.80 beta) (6040x1080, TriMon surround setup)
installdisk for FF, Samsung 830 series 256Gb SSD)