Healer for first time

[Anarism]

Honestly, in terms of learning healer, I'd argue AST is easier and the two reasons for that are Essential Dignity and Lightspeed. Having instant heals aside from Swiftcast helps a lot to compensate for mistakes while you're still learning the damage potential of packs, especially if you get a wall-to-wall sprint tank not using their CD.
Of course, AST is also a lot more boring than WHM in early dungeons because your dps is a lot worse and you can't even play your children's card game until Haukke.