Offizieller Kommentar
@Jamie > Sorry to hear the crossfader curves don't match your preferred curve. For your reference, there's no such thing as a "true crossfader" curve, as virtually every piece of DJ kit out there with a crossfader has a unique curve.
As an entry-level unit, the XDJ-RR only features 2 different cross fader curves, plus "thru"; Constant Power, and Sharp Cut. In Constant Power, the curve is such that at the mid-point of the fader, the level from each channel would sum to have the same output level as one single channel by itself at either end of the fader - in other words, the combined signal from both channels should sum to the same level across the travel of the fader. The Sharp Cut curve is designed for full power from both when the fader is not at the extremes of the travel, intended for a quick and hard cut in for scratching.
Unfortunately there's not much else you can do to adjust the curves, either in the software or hardware.