The low score of the Leica CCD doesn't surprise me. But, I do think DXOMark's test results have always been skewed (as do most of us Canon people).
And I still don't understand why so much emphasis is placed on dynamic range, color fidelity, and low noise...at low ISO levels. On any modern full frame camera (regardless of brand...well maybe except for Leica, haha)...the noise is so low below ISO 800, that it's extremely silly to worry about it. Even the noise on my 5 year old XXD body is so low below ISO 640, that it's almost absurd to think about. Autofocus performance and lens sharpness are really the only things left to think about, at the low ISO's. I get basically no detail loss at all, due to any obsessive NR I might dial in, in this range.
I mean, if we're going to worry about the noise and dynamic range of a sensor at the lower ISO range, then we're really talking about small, point-and-shoot sensors (and to some extent 4/3 sensors)...but definitely not huge full frame sensors.
What counts most of all for me, is the noise performance, and how I can maximize it, above ISO 1000 (since I enjoy doing nature and wildlife shooting, and don't use strobes very often). And starting around this range or a little above it...all of Canon's full frame sensors, pull ahead of all Nikon's sensors save one, the D4 (or the older and "better" D3s with its bigger pixels).
Perhaps sensors will see a revolution of improved performance soon...or perhaps not. I'm still mostly happy with what I've got now, as humble as it is.