I checked out 3s today just to see how it was.

I noticed while 3 boxing Mogushan vaults on 25 man mode the spell effects got to be rough ( 20 fps ) on spiritbinder. Warspear was much lower about 30fps on a good spot.

At this time it appears 1 instance is almost twice as demanding on this resolution for the GPU. Makes sense. I dropped the main down to 'good' settings and that brought the main back up to 55-60FPS in Warspear.

Probably due for a GPU update pretty soon. I will say 3440x1440 and 4K are both going to require a very expensive GPU to multibox.