As I understand it, the goal in adjusting azimuth is to minimize crosstalk between channels. This means that the amount of crosstalk will not necessarily be equal for both channels (in fact it almost never will be equal) but merely that it will be as low as possible for each channel. The goal is not to achieve equal crosstalk but rather minimal crosstalk. (This usually involves a compromise in my experience doing it with a Signet cartridge analyzer and a test LP; when you get to the lowest crosstalk for one channel, the crosstalk in the other channel is frequently unacceptably high and can only be reduced by adjusting azimuth further, such that there is some small sacrifice in the db of crosstalk for that first channel one measured.) As one plays with azimuth by ear crosstalk reaches a happy medium, which we hear as "good soundstage". I am not familiar with the Feickert method, but if indeed it does allow one to measure and minimize crosstalk, it should work to bring one closer to "goodness" (optimal soundstage). The fact that nearly all cartridges will have slightly unequal outputs between channels will have no effect on this process, although it probably has a small effect on the actual numbers of db one measures. This is assuming that no cartridge that is not "broken" will have more than a 1.5db or less difference in absolute output between one channel and the other. Ergo, I would say that DT is off-base in his statement that one must know the difference in output between channels (which anyway one could measure) or that a cartridge has to have perfectly equal output between channels, to properly adjust azimuth using an electronic device.
One of the main reasons I bought my Triplanar many years ago was the demonstration of the effect produced when azimuth is properly adjusted and the ease with which this goal is achieved using the TP. I am really rather shocked to learn that the DaVinci has no provision for this important facet of tonearm function.