Aside from your own blah-blah, the reference link you provided, the same distinction obtains at Base ISO:
The truth is, they're all getting close, but Nikon's oldest is still a little better than Canon/Sony's newest.
You can't argue with measured numbers:
Landscape/studio cameras at low ISO: http://photonstophotos.net/Charts/PDR.htm#Nikon%20D810,Sony%20ILCE-7R,Sony%20ILCE-7RM2D810 at ISO 64 - 11.6 stops (setting the floor at 20:1 SNR - DxO uses a 1:1 SNR, which is why the numbers are different, but interconvertible)
A7r at ISO 100 - 11.71
A7r2 at ISO 100 - 11.42
All within the same roughly one-third to half-a-stop margin of error (i.e. equal performance, likely variable between individual sensors and indistinguishable in practice). The A7r2 also nets you a few extra megapixels over the other two - never a bad thing for a landscape/studio body.
D810 at ISO 100 gets 11.06.
So, if you really want to nit-pick, the A7r actually recorded more DR at ISO 100 than the D810 did at ISO 64. Not that this actually means anything, since the two values are so close together they are likely to fall within the test's margin of error and would be overshadowed by sensor variability in actual use. Both Sonys also overshadow the Nikon at ISO 100, but you'd have little reason to ever use ISO 100 instead of ISO 64 when shooting a static scene with the D810, so that comparison is irrelevant.
Action cameras at mid ISO (400-6400 - the most relevant ones for the vast majority of action/wildlife/sports photography): http://photonstophotos.net/Charts/PDR.htm#Canon%20EOS%201D%20X%20Mark%20II,Nikon%20D5,Sony%20ILCE-91Dx2 at ISO 400 - 9.56
D5 at ISO 400 - 9.00
A9 at ISO 400 - 9.22
At ISO 400, D5 and A9 are essentially the same, with the 1Dx2 a little ahead.
1Dx2 at ISO 800 - 8.86
D5 at ISO 800 - 8.43
A9 at ISO 800 - 9.24 (different post-sensor treatment at different ISOs likely provides the jump in DR seen between ISO 400 and 800 - we see this at a few points in the graphs of all three cameras)
The A9 and 1Dx2 are comparable here, with the D5 over two-thirds of a stop behind the leader.
1Dx2 at ISO 1600 - 8.06
D5 at ISO 1600 - 8.04
A9 at ISO 1600 - 8.49
1Dx2 and D5 are indistinguishable here, with the A9 possibly a little in front.
1Dx2 at ISO 3200 - 7.14
D5 at ISO 3200 - 7.60
A9 at ISO 3200 - 7.44
D5 and A9 are essentially the same at ISO 3200, with the 1Dx2 lagging a bit behind here.
1Dx2 at ISO 6400 - 6.18
D5 at ISO 6400 - 6.68
A9 at ISO 6400 - 6.53
Again, the D5 and A9 are essentially indistinguishable, with the two values falling well within the margin of error, with the 1Dx2 again being a bit behind.
So, all three sensors provide comparable DR performance for the vast majority of sports/action/wildlife applications, with the 1Dx2 being perhaps a touch better at the bottom of the range (if you shoot outdoor daytime sports or in floodlit stadiums) and the D5 having an edge over the 1Dx2 at the top of the range (if you shoot amateur sport or indoor sports with poor lighting) and the A9 being consistent throughout the range. The A9 gets you 16% more pixels, but currently lacks fast, long lenses (fine if you shoot tennis or basketball, not so great if you shoot soccer or hyenas), although this is likely to change by the end of the year, with a fast 400mm in the works.
As an aside, here are the values for the D810 and A7r2:
D810 at ISO 800 - 8.44
A7r2 at ISO 800 - 9.32
D810 at ISO 3200 - 6.59
A7r2 at ISO 3200 - 7.37
Obviously, they're not action cameras, but, as a general-purpose camera (which almost all cameras, whether landscape-oriented or action-oriented, will be called into service for), and even for some limited landscape/nature situations (e.g. avoiding star trails, or where a tripod isn't an option, or where you're trying to shoot a macro of a flower or fungus and there's a breeze), the A7r2 is well ahead of the D810 at mid-to-high ISOs. Between the D800/D810/A7r sensor (all variants of the same sensor) and the A7r2 sensor, Sony really gave a major boost to the high-ISO performance of Exmor (which was even more of an issue back in the days of the A900 and D3x, which were great at base ISO, but not much good above ISO 400 or so).
Even
against the D5, the A7r2 sensor holds up well at high ISO - it retains a DR advantage up to ISO 2000, then becomes indistinguishable with the D5 after that (the lines go back and forth and cross several times, but stay within 1/3 of a stop of each other). It also retains its megapixel advantage - over double the pixel count. Of course, the A7r2 probably won't autofocus under those lighting conditions, but the sensor holds up all the way to very high ISOs.
Extremely high ISO (not actually all that relevant for most purposes, other than bragging rights or if you exclusively shoot in unlit environments, e.g. poorly-lit concerts): http://photonstophotos.net/Charts/PDR.htm#Canon%20EOS%201D%20X%20Mark%20II,Nikon%20D5,Sony%20ILCE-91Dx2 at ISO 12800 - 5.2
D5 at ISO 12800 - 5.68
A9 at ISO 12800 - 5.58
1Dx2 at ISO 25600 - 4.28
D5 at ISO 25600 - 4.72
A9 at ISO 25600 - 4.61
1Dx2 at ISO 51200 - 3.51
D5 at ISO 51200 - 3.69
A9 at ISO 51200 - 3.50
1Dx2 at ISO 102400 - 2.72
D5 at ISO 102400 - 2.70
A9 at ISO 102400 - 3.17
So, the A9 and D5 are indistinguishable at ISO 12800 and 25600, both being marginally ahead of the 1Dx2, but all three are equal at ISO 51200. Interestingly, the A9 jumps ahead of the other two by a significant margin at ISO 102400, but, by that stage, the image quality is so poor it's no good for anything other than a casual 'I was here' shot, or a 'breaking news' shot taken on the scene of an incident by a photojournalist, where any shot is better than none.