Main Dog,
If VR was limited by 1.05 Vmca, V2 would increase with it, because V2 cannot be less than VR plus the inevitable speed increment between initiation of rotation and 35 feet with one engine inoperative, which is greater at the higher thrust setting.
However if, as you say, "V2 speeds on the 744 are essentially independent of thrust rating (as they are always well in excess of the minimum required 1.1 VMCA)", then it is unlikely that VR is limited by 1.05 Vmca.