I really don't like DXO. I really DO like personal reviews and their images, this tells me more about a lens. Personally I have owned the 135L and there is no flaw, F2 is dead sharp, accuracy results in never a missed shot. You can shoot at F2 and never worry. I only like it on FF personally unless its for sports. The thing is I had the 70-200 too and I was carrying all this equipment and for what? I never or at least can't recall a single shot that didnt look spectacular. The weight is so much nicer than 70-200 and the build is very solid. The glass looks just like my 85L II thick and heavy, not the lens but the glass. You kinda need to expect to be doing head shots and the like more than anything so if you don't shoot stuff like that you might not like the focal length. I recommend getting a plug in for LR4 and having it tell you what focal lengths you use most.
I use this plug in, it tells me focal lengths used. It took a while to read everything but i had it go thru all my wedding photos to determine what lenses i'd like ot limit myself to using given how i used the lenses i have owned.http://regex.info/blog/lightroom-goodies/data-plot
He does ask for a donation and its totally worth it!