One of the reasons I decided the D8xx series was not the camera for me. I consider them rather specialized and I'm not a specialized photographer
I'm not so sure I agree with that statement, I'd say the D810 is much more of a versatile camera and the reason I chose it over the D750.
My photography is a mixture of Wildlife and Nature which includes both landscape and night time.
I have the extra pixels for flexibility with cropping, the high pixels for very detailed landscapes, ISO64. I do sacrifice a little on the high ISO that the D750 gives, but not enough of a concern to drop the number of dots for the wildlife. I do shoot up to about ISO4000 without having to worry and DXO Optics makes life a lot easier.
Personally for me, it wasn't the fact that the D810 didn't perform well at high ISO, it was the fact that Adobe's RAW converter isn't great at processing them, any shot I do at ISO1200 and above, I always run through DXO Optics as it comes out clean. Adobe (LR and Photoshop) really fails as a D810 converter.
I agree though, it was a real tough decision against 2 amazing bodies, but it was the number of dots that made me go for the D810.