While that's a mostly viable "skills ladder", what I often see if people who can whip out a few dozen slack line tricks REALLY well, but have foresaken the skills required to fly precisely...
If you take a dozen AKA compulsory maneuvers and ask a dozen fliers to fly all of them, a fair number will be able to do the tricks really well but can't carve clean maneuvers.
What I'm indicating here is that a "skills ladder" may not be linear (i.e. A to B to C to D), but may be better addressed as independant skill areas.
In my personal observations, a fair order in which to learn is:
Flying > Landing > Turn Methods > Precision > Edgework > Stalls > Spin Moves > Pitch Tricks > Combos
Certainly, this order would put all the skills in the right order for a flier to develop the in most well rounded way possible.