I figured it wasn't a good sign when the game almost came to a complete stop shortly after starting OWB. It looks like your engine is running out of memory (again) and constantly swapping to disk whenever the player is in the outside environment. It's not too horrible until there are one or more NPC's in the scene... then the frame rate goes down to about 1 frame every 2 seconds or so. Battles are just unplayable.
I was hoping it was just a passing thing, but no - it happens pretty consistently, even after restarting the game. My character is at level 40 and my save file is about 12MB. I imagine most other people playing this DLC are in about the same situation.
Do you guys do any play testing at all?
As usual, artistically the game seems very compelling. Technically it's another failure.
It's not like this is the first time you've had precisely these problems with your engine...