I can't imagine any pro photographer who is about to lay down £10K for their new mkII white lens will give any consideration to the DXO fantasy lab metrics.
We all know that 400IIL is optically as good as the mkI but weighs a lot less. We all know the 500IIL is stupidly light and slightly better optically to the mkI (although i've never found the mkI lacking). We all know that the 600L wasn't the critically sharpest of the big whites when wide open (but still very sharp) but the mkII is noticably sharper. So what's the point in passing these lenses through their labs? They didn't bother with most of the mkI lenses.
With the mkI lenses, I felt that the 400L was the most versatile. It's one of the sharpest lenses ever to come out of the Canon stables and it took 1.4x and 2x converters better than most lenses. But it is very heavy, like the 600L. With the mkII lenses, while the 400IIL is just as versatile as the mkI....it's a lot lighter. But the real star in the current mkII line up (in my opinion) is the new 500IIL. It's SO light it opens a lot more options for handholding and is far easier to move around with it. Sure the new 200-400L looks nice, but it's very heavy and not much lighter than the 400IIL. Given the choice I'd go for a 500IIL or a 400IIL or a 600IIL in that decending order.
My opinion on DXO labs hasn't changed over the last 4 years. Their weighting for their point scores are heavily swung according to their own internal brand bias.