certainly seems to be something with specific structures on the map. Sitting at the Hawthorne Hut crystal, looking outward from the camp it's 50-60 FPS everywhere I look. Turn and look down through the tents... and it drops to around 40 FPS. Ran over to Little Solace and panned around. When I looked in the direction of Hawthorne Hut---38-40 FPS, anywhere else it was the same 50-60 FPS.

Strangely enough though, the tents in Little Solace didn't cause any problems... it appears to be something specific to the Hawthorne Hut---and it doesn't appear to be the crystal, as I was standing with the tents to my back and looking at it and was locked in at a steady 55 FPS---but when I turned around to look at the Choco Keep's tent it dropped to 43 FPS. Moved into specific tents, and while it fluctuated a little, it wasn't dipping to 40--but when I moved to just focus on the hut itself, it was 38-43 FPS.

So, it certainly seems like some (if not all) maps may have very specific "hot spots" on the map that are affecting frame rate when your view is pointed in that direction.