There is some explanation for the so close DxO scoring of the A7RII vs Nikon D810, while the real sensor improvement is a bit higher IMO:
- Nikon managed to implement real ISO64 boosting maximum dynamic range
- The A7RII on the other side has increased robustness at high ISOs, probably because it is more video oriented. In fact the behaviour of the A7RII is in the middle point between the A7S and a genuine "ISOless" sensor
- DxO final scoring weights dynamic range a lot. This is the reason why Canon scores unfairly low in the DxO benchmark. I never look at those figures but go straight into the detailed plots.
In brief, while the D810 is still the best performer when set on a tripod, the A7RII is a more balanced camera with outstanding resolution, dynamic range and low light capabilities. More than that single point score could reveal at a first glance.
Regards