In my testing at diamond city elevator, you know the spot right? Most of the lag I got was because of ultra shadow distance and when it's on medium it was a 20+ fps increase in this area. I also have managed to get sli working using the batman city bits so try that if you have two nvidia cards.
0x080202F5 (Batman: Arkham City)
75 fps (I use this cap since I have a gsync monitor)
SLI_GPU_COUNT_TWO (All these options below should equal the amount of cards you have)
SLI_PREDEFINED_GPU_COUNT_DX10_TWO
SLI_PREDEFINED_GPU_COUNT_TWO
These setting when applied in nvidia inspector give me a 30+ fps increase! On two gtx 670's a [email protected], 12gb ram I get 65 - 77 fps (on ultra apart from medium shadow distance, lighting to medium, godrays to low, standard dof and motion blur off. The only sli bits problem is the character blackface and then with the menu and pip boy text getting a little corrupted, imo it looks a part of the aesthetic of the game, hehe.