I have no reason to doubt the accuracy of DXO's test procedures. Nor have I seen any real world comparisons between the P65+ and the D3X demonstrating that the DXO test results are flawed.
nor have anyone posted any real world comparisions demonstrating that the DXO results are correct!
I've once compared a Sony A900 to a P21+ because I was looking for something to shoot with at ISO400 handhold (with my P45 that's actually impossible).
I ended up buying the P21+ for... well, for many reasons.
DR? I don't know... I only know that the P21+ "saw" much more, especially in shadow areas.
Here on the forum there was a comparision D3x with AA Filter, D3x with AA filter removed and P21+... unfortunately the link is not available anymore.
The P21+ was clearly suprior
if (!) you like that clean and clear, bold look MFD produces.
That having said the RAWs I've seen from the D3x look very, very good. But simply not as good as MFD.