SLI/Crossfire scaling in ARR?

[Pseudopsia]

All other games I got on my PC runs way better than when I had the 6950. So why did ARR perform alot worse

Here's the technical answer:
The problem with ARR is it has the same executable name(ffxivgame.exe) as FFXIV 1.0 so Nvidia drivers chooses FFXIV 1.0 game profile. ARR is a new game engine so the FFXIV 1.0 SLI settings are incorrect. This is why SE is telling you to turn it off.

You can use Nvidia Inspector to modify the game profile, you can try changing the SLI compatibility bits to a different game to see if you get better results.