I haven't had enough time testing it , but wit the current ccminer v7m7 , the results with the XCN are not so well. Its about 10MH/s but it should be twice better - my opinion...
twice would be a lot... knowing that a 780ti does only 14mh/s
You can get already a little more by overclocking the memclock of the p2-state to its maximum with nvidia inspector (which is 3500mhz and correspond to the nominal memclock value).
I will publish soon an update to use better launch parameter for the 980 (because for the moment, it just picks those of the 750ti), my 980s are doing around 12.5MH at the moment...
My Gigabyte 970s say P2 as well.
I may have stumbled on a common thing though, these are all 3rd party tools. Nvidia inspector, Precision X, and afterburner all said my cards were running at 73% utilization, but When I go into Geforce experience and click on led visualizer, and then GPU properties, it shows them at 98%, 78C, and 3000+rpm fans. I have them with a 750ti all crammed in my case, otherwise I'd run the fan curve differently.
(I don't use geforce experience and don't know where other system monitoring is if it's in there or another nvidia tool)