I guess there just are a number of places where your video-card might and most possibly will choke. Afcastle is not one of the places for me though. The most terrific fps drop I had aroud the place with Keds where the Fate with giant boar take place. Urth's fount if I remember right. When I set tesselation to High fps immidiatly goes down from 60 [I play with 60 fps limit not to overheat videocard] to 20, although all the DX11 cookies set on max altogether in other random places could only kill 10 fps, lower it to 50 [in worst cases], that is.