I main AST. It is literally no harder than any other healer in the game.
Cards? There's 0 thought to them thanks to SE's screw up starting in Shb.
Tab Targeting? It is crap in this game since it doesn't go left to right from the get go, has issues with targeting the boss anyway on tall/small characters and is only an issue because SE refuses MO support or some better party targeting for controller aka out of the player's hands.
Delayed healing? Exaltation is a press and forget. Macrocosmos is a capstone ability and therefore not applicable in ~90% of all content. And Earthly Star? Why the hells does it matter if I mess up its timing when I have no less than 4 other abilities one being on a GCD if I so incline that can easily cover it's place to where I don't need to use it outside of a DPSing tool because SE made it so my kit invalidates itself....
Like. Ever. Other. Healer.
Unless you're going to tell me that HoTs require thought when they are also a "press and forget" ability and one that every healer also has.
tl;dr - when you get good at one of these jobs you can literally switch to any of the other 3 because they don't play that much different from one another ergo the roll is easy. Or braindead I suppose the argument is.