Hi,

I have 3x 980ti cards running in my workstation. While rendering i noticed that all of them have a very unregulary gpu usage. (see image)

i have "use priority" unchecked for all cards . What could be the reason and how can i fix it?

Cooling is also not the issue, I have two hybrid cards and ...

6GB should be more than enough for nearly any Project. I have never had a cinema file that exceeded 6GB and if so you could optimize it by splitting it.
As you can tell from the Breakdown, Raoul Marx used a 780 ti and a 680 with only 2-4GB of vram to pull of the semi permanent titles on his own.

So ...