I can not agree that 1080Ti is beaten by 1070's in Equihash. For some reasons Sols per card are related very close with retail prices (at least USA prices) so:
1070 - 475 sols average = 475 USD
1070Ti - 530 sols overclocked = 530 USD
1080 - I can squeeze 570 average (592 max) sols. This is the most sweet spot I think.
1080Ti - 750 Sols = 700-800 USD
So basically they are all really close to each other
1060 - 330-350
1070 - 480-500
1080 - 580-600
1080ti - 730-750
this is true. the best ROI - is 1060, but profit is really small, next card - 1070. 1080ti little but worse than 1070.