NV DX12 support is not as good as the DX11.
And that means any Pascal card has same issues, even the GTX1080Ti if ever comes out.
Here is my results on the TW Warhammer.
1920x1080
Score 77.2, GPU 1080 @2190/2762, CPU 6700k @4.8, Panos DX11 Link 372.90 Drivers
Score 66.2, GPU 1080 @2190/2762, CPU 6700k @4.8, Panos DX12 Link 372.90 Drivers
2560x1440
Score 50.5, GPU 1080 @2190/2762, CPU 6700k @4.8, Panos DX11 Link 372.90 Drivers
Score 41.8, GPU 1080 @2190/2762, CPU 6700k @4.8, Panos DX12 Link 372.90 Drivers
And that is representative of all DX12 games with my 1080.
DX11 is better......
Or Kaap's results at 2560x1440
Score 66.8, GPU TitanP @2126/2728, CPU 6950X @4.4, Kaapstad DX11 Link 372.70 Drivers
Score 56.4, GPU TitanP @2126/2728, CPU 6950X @4.4, Kaapstad DX12 Link 372.70 Drivers
While have a look at AMD cards, barely any loss of fps, for sure not 20% the NV cards have.
Score 39.2, GPU Fury X @1190/500, CPU 5960X @4.4, Kaapstad DX11 Link 16.9.2 Drivers
Score 38.8, GPU Fury X @1190/500, CPU 5960X @4.4, Kaapstad DX12 Link 16.9.2 Drivers
Score 37.7, GPU Nano @1100/550, CPU 4690k @4.7, Radox-0 DX11 Link 16.9.2 Drivers
Score 36.4, GPU Nano @1100/550, CPU 4690k @4.7, Radox-0 DX12 Link 16.9.2 Drivers
Score 29.0, GPU RX480 @1380/2200, CPU 6950X @4.0, Kaapstad DX11 Link 16.9.2 Drivers
Score 28.0, GPU RX480 @1380/2200, CPU 6950X @4.0, Kaapstad DX12 Link 16.9.2 Drivers
(Please bear in mind that the settings for all above is AA 8x and ultra)
And we ain't going to see Volta until 2018 now, as NV announced. Just a rebaged 1080/1070 for 2017, leaving AMD open field for Vega.