Like the OP, I ran into cone wrenches that were too thick for the flanged locknut on Shimano hubs (XT M760). I think I found that the maximum thickness cone wrench that will fit that locknut is right around 2.0mm.

The thickness of various cone wrenches I have include:

Park DCW: 1.85mm

Park SCW: 2.15mm

Park CW: 2.45mm

Tacx: 2.05mm

Hozan: 2.00mm