I've been meaning to respond to this thought of how I could for a while now and ultimately decided on my experience alone (note- Diurnal AST when I got accessed to it in HW):
From start to finish in... 5.08? I think I started (somewhere along there... maybe?). I was able to heal all MSQ content (so required dungeons raids and trials) with GCDs, ED, and the occasional CO and CU.
I didn't learn to use the rest of my kit until I purposefully tried using it over those abilities (and I got more tanks who were wall to wall pulling).
Now knowing how to use my entire kit, I still don't. Why? Because Horoscope, Neutral Sect, and Collective Unconsciousness are 100% unnecessary when I have Earthly Star and/or Celestial Opposition. I literally have to force myself to use them over the other two because all of them share the same recast timer of 60s (bar Neutral but I don't need its shields anyway... nor want them) and out going damage is scripted enough that if every one plays perfectly I'll always have ES or CO up.
I have more fun at 70 and sometimes 60 than I ever do at 80.
This isn't including EX and Savage and lv80 Alliance Raids... but even still
Take that as you will.