i think the title should be "More Mechanical Advantage Climbing Line"; for we should see that the DdRT has a 2:1 potential as is(we have to shift half our weight x distance to the control side, to lift the load side etc). Then we must see this to be able to discern form visible thru all else in the same closed system efficiency examples in pulley (or 1st class lever) systems.
FireAxMan offers a solution of more ergonomic in trade of mechanical efficiency; as long as the CG (lower chest as center of gravity) is kept in line with device(rope).
We can also have climber pulled up/ or aided with rigging line as they work their lifeline separately thru self tended hitch as the are prussicking/camming up. The rig line can be worked to take 50%-70% load off climber, the life line provide final lift, and safety; this way rig line moving at full speed (of input); doesn't outrun climbing moving at half speed(of it's input; the 2:1 power increase, having half speed as reciprocal).