The latest nvidia driver adds SLI profile for Fallout 4, and yet with my two 970s it still tanks completely when I enter city areas and ultra shadow distance. I think we can rule out GPU. This is a CPU issue and still isn't fixed.

EDIT: I'm not sure but actually I think I'm wrong. I saw some sites reporting it gave SLI support but I still see the lense flare bug when I use SLI and the game is mentioned nowhere in the drive rnotes.

(i'd delete this thread but I can't find a freaking delete button)

No, the problem isn't a CPU issue. There are people on the nVidia forums that say the current drivers give negative SLI performance and their previous SLI bits that they messed around with in nVidia Inspector gave much better FPS:

https://forums.geforce.com/default/topic/894480/sli/fallout-4-sli/10/?offset=149#4744469

The problem lies on nVidia and Bethesda.

Added your thread to the collection of threads complaining about this issue that Bethesda loves to ignore:

http://www.gamesas.com/topic/1554098-bethesda-you-need-to-patch-the-game-to-support-nvidia-sli/

it also makes terminal locking character in place worse. Like every time.