Well to me there still seems to be something not being right.
My issues come close to those of oxa1900. Made a thread.

http://larian.com/forums/ubbthreads.php?ubb=showflat&Main=79817&Number=638013#Post638013

I still find it weird that Arx for example drops insanely in FPS (in the city) or any behavior i described during combat. (Hitting and enemy sometimes stutters and sometimes not.) Other games run perfectly fine (I mentioned FFXIV for example during a giant raid with tons of people and enemies no drops at all).
There was mentioned in the thread i made what my memory usage could be. I will check that out. But 16GB should be enough for only an OS and a game running....