Question about these results
I'm an owner of EF-S 17-55 F2.8 IS USM and 70D. I'm disappointed at the results shown here, because EF-S 17-55 F2.8 IS USM is the only flagship zoom lens for APS-C DSLR and some of the other reviews have given it quite a credit as being comparable to the full-frame 24-70 F2.8 L II in optical performance.
Could it be that the poor result is due to "focal point shift", a common issue seen by many Canon lens. For example, my own EF-S 17-55 F2.8 IS USM needs a "plus 4" micro focus shift adjusted in 70D to achieve the best focusing.