Dude, I have all the problems the OP has mentioned and some others have agreed with. AAAAAANNNNNDDDD, I have a BRAND NEW i7-3930 on an ASUS X79 Pro on windows 64bit with 16GB of Ram, and TWO GTS450s with a gig of ram EACH in SLI config for this game.
I still get random and inexplicable FPS drops while out doing missions with no one around. There are clearly certain areas of the maps that induce this problem. As I approach them the FPS drops like mad, and then as I leave it returns. If I go back in, the FPS drops again. This has happened Taris, Tatooine, Alderaan and Balmorra (toon is only level 35).