I have all the setting on high in-game except. Bloom - off, Shadows - off, and tree/grass quality to 50%, everything else is to very high.
My performance doesn';t change based on my settings.
Oh I meant with lower settings that you have in the nvidia control panel (not in the swtor itself) the GPU usuage should be low.
I'm guessing you've already deleted DiskCacheArena, run repair, defragged, and turn your anti-virus off when swtor is running as well? From the improvement that you got changing that Windows setting, my suspicion is that there's a background program or service that's doing a number on you.