Almost the same story with my nephew. Both his WAR and PLD are 60 and 50 respectively. He wanted to give healing a try so he unlocked ast. He might have more XIV experience than I, but he does not have more MMO and healing experience. So I advised him that he level cnj first. I also advised that he level sync down and repeat the first three dungeons when mistakes are much more forgiving. He has little interest in the pet micro management from acn/sch.

He did not take my advice. He had a couple of wipes before deciding to get protect from cnj, and got his ast to about 44-ish before giving it up. He wants to try cnj now, and I warned him that he will have to level acn as well if he plans on being a whm.

If you want to be a good healer, don't take shortcuts. Start from the beginning. Especially if you've never healed in an mmo before. If you decide to level acn as well, you'll be queued as DPS, but don't let that stop you from casting physick. Get used to looking at those HP gauges.