I can confirm that Helifax's fix worked for me. I didn't think you could plug all connections into one card and have surround work, but it did and The Witcher 3 worked. The second card jumped around 80-90, while one stayed at a solid 99. So scaling is still being weird. The new drivers in general give me weird SLi performance and most games I played. Battlefield 4 is doing the same scaling, where i get 99/80-90, the frames seem there, but now I'm getting artifacting, and Directx crashes (which could also being the game itself). Wildstar - 90+/60-70 (but the frames seem there).
BUT, before I plugged all monitors into the one card, on these drivers (352.12) I got the reduced scaling in all games mentioned and more, but plugging them into the one card fixed it for those games....somewhat. Now it's easy to test if the artifacting and directx problems I'm getting are driver related, by going back to 350.12, which seemed to me to be the last good driver, that I have had no troubles with (but no Witcher 3 flag).
UPDATE: Just tried to run Dragon age: Inquisition and I got the same directx error with Battlefield...got to be the drivers :/
UPDATE 2: Ok, so I switch back to using connections in both cards, and The Witcher 3 goes back to 60% in surround, BUT it gives me 90+/80+ when I change settings in-game to single screen - which it wouldn't do before - I had to turn off surround in NCP, so that's a bonus...and also probably means they've done something in the new patches.
UPDATE 3: So I loaded up Dragon age and Battlefield 4, and no direct x crashes. BF4 scaling seemed off, but then it got better. I really don't know anymore
My mind is scrambled from looking at scaling constantly since The Witcher 3/Nvidia drivers release.