Andrew R Stewart 

I will take a different view here. Should disk brakes rub? No. when riding in a straight line and applying even pedaling pressure. But when cornering or putting the pedal to the metal it's not un common. What is the issue is that the clearance between pads and rotor is far less the rim and pads. Less then the added lengths involved, axle to pad contact points. This is why all the new axle/drop out standards are changing. The old standard od a 9 or 10 mm axle with a QR having a 5mm shaft diameter was plenty stiff enough for the caliper/canti/V brake pad and rim gaps when stresses flexed forks and rims. But now that those pad/rotor gaps are so much less a stiffer axle/frame design is needed.

Hydraulic lines only make the initial squeeze smoother and the modulation better, nothing to do with the pad/rotor gaps. The closer gaps and the resulting rub when the system isn't stiff enough is part of the industry learning curve. That our engines are only a half horse power or so make this rub less acceptable.

So the current answer to your real future is to get a bike with stiffer wheel/frame/caliper interfaces, and live with the results. Andy.