edit: may not be same issue you're experience, try walking away form roach. i notice your fps drops slowly as you ride away, then when you ride closer again, not sure if thats due to your camera angle or something in the video.
well i tried to repro it again, but can't.
must be an nvidia thing.
ok, i was able to repro it on horseback...
been doing it on foot this whole time
however, it seems to occur as soon as i get on roach.
insant drop from 42 to 35 fps when mounted...
fps doesnt go back up until i walk away from roach.
when i return, the fps is as normal, even when looking directly at him.
mount, and again, fps drop.
so it's a roach issue.
actually, if i get the camera real close to him, i can get 36 fps...
so it's just prob the horse model. no bug here.
then when you walk away, the LOD drops.
i dunno, seems like an expensive horse model, even in my case, that's a 20-25% drop (6-7 fps), no hairworks.
other areas of novi, not as drastic, from 39/40 fps to 35-36, about 10% drop. tested open wilderness too, about the same 3-4 fps drop. so it's just that one area, not sure why.
anyways, if it's not the roach issue, then must be nvidia-specific, cuz i can't repro anything other than that.
only other thing i can see is, that area is a bit more taxing when look at the archway (with 4 braziers), but not by much, maybe 5%. yours seems to slow down on the small arch to the right though.
hmm, may have something to do with lighting conditions too. not seeing the same 20-25% drop during day as before (during morning/eve). at night the archway drops even further due to dynamic lighting from the braziers.
well, i'm out of ideas. that large drop may just have been due to the angles i was looking at before/after mounting horse. can't see it being anything much other than that, with some minimal lighting effect. maybe 10-15% performance drop on horseback.
in your case, losing about 20% fps, 75-80 down to 60-65. try walking away from roach, or post same video on foot.