What's scary about this video is that they didn't actually go to anywhere that the framerate really drops.
The 20fps drops seen in the video on the Great Plateau I noticed at the time but considered them 'acceptable' - because I'm not very framerate sensitive.
But there were at least three entire areas in the game where I found myself thinking 'This is not acceptable.' And I'd wager the framerate there is in the mid-to-low teens at times.
Yeah...they need to test villages.