It started getting lag in Act 2 at the Last Light Inn and or surrounding shadow areas, into the toll house after patch 4. Even quitting to the main menu would keep the video lag on the grassy overlook and menu /options on PC in patch 4... I would restart the whole game and could get small spans of decent frame rates. Went back to patch 3 hotfix 9 and things were smooth again. All I see mentioned is act 3, but it was clearly effecting more than that. They did seem to word it that "by act 3" things became horrible, so I am hoping that that means they still noticed as the game went on it got worse and worse... I should have tested a new game from act 1 to see if I still had issues there... But I feel like the proof is that when I went back to the last patch, things returned to normal as far as performance goes.