I think it is just the video card. Check the performance in the Cyseal marketplace; that is the worst case situation in the game (a lot of NPCs around with various AI, the fountain and a lot of objects, etc).
I don't know if there is a way to avoid a crash caused by disabling texture streaming (don't recall seeing reports of that being an immediate issue). Try lowering the graphics quality (at least the texture quality) and maybe the resolution, and/or switch to fake fullscreen or windowed mode.
