Its a SWTOR related problem. They sadly licensed an incomplete engine back then.
Best you can do is try it with an SSD, a lot of people who say they run it fine are running it on a SSD.
Im going under 30fps in Ops, WZ, FPs and rarely even just in random battle on a planet.
Even 15fps in a heavy OPS or WZ.
And that is with a:
i5 3570
GTX 970
8GB RAM
1,5TB HDD
No matter what settings i have.
Meanwhile AC:Unity runs stable 30+ fps all times on Ultra with x2 MSAA 1080p.
Dont try contacting support about them, i did. I told them not once that i only have bad performance in SWTOR, everything else runs perfectly.
They still said it that its a problem with my PC.(i've read on the forums that others have been also told this)