Well I'm playing in 1080p, no AA or AO on a 770 and my frames dive to 36fps looking in certain directions in Demon Ruins (where I was at when I made my post). I haven't played Blighttown yet since I'm way past that area.
I know this is a hack and I don't expect it to be perfect, I was just curious if there's something I can do. At the very least I know I can never go back to 30fps for this game, and I used to cry tears of joy that it was a locked to 30 in the first place!
Demon Ruins is one of the most intensive areas for some reason, I have the same issue. Chalk it down to bad optimisation I think.