After having some issues with my 17-40 and having it to be repaired and then sent back again, I started testing my lenses in real world situations with some scientific reasoning/experiments. I was never much of a brick wall fan, so if it seemed to do what I wanted, I was OK - which is what got me into bother with the 17-40 after moving to FF.
But anyway, that's an aside, the one thing I really learned from all this is that each lens has a very definite set of characteristics that cannot be dumbed down into 1, 2 or even 3 numbers. Or even the center, mid center and a corner on a (flat) test chart.
For instance, no test chart or DxO score tells me how quickly the resolution of the 17-40 drops off compared to say a 24-105 at 24mm f11. (No, even a test chart does not). In fact the more I actually look at real images, the less the lenses seem to be properly characterized buy the test scores even when I can see how those were obtained.
Point is modern lenses are complicated, they have a lot of glass and a lot of corrective elements that make things that should be simple (like DOF) more complicated. Unless you are shooting wide open in the center or at f22 (no wait, not all lenses are the same at f22 despite the fact that every lens should be equally mushy from diffraction)........no, no not going there.
Blah. Rant over. DxO, photozone, blah. Maybe good for a quick general 'is this a lemon' glance, but even then I'm suspicious. All those numbers for people to read so much into, reminds me of the difference between precision and accuracy.