I don't heal a ton, but when I do I typically play Astrologian in raid content and Whm in dungeon content.
White mages are overpowered in dungeons due to its kit and mostly due to the fact Holy has a stun and well gravity doesn't get crap. The ability to stun lock mobs for nearly 12 seconds is massive. You save so much potency of healing by not having to heal anything.
In raid content my go to is Astrologian and always has been. Personally I have always loved this class, when it was bad during HW, when it was great during SB, and now that it's meh in ShB I still love this class.
This class is just gorgeous to play and I love the fact that it's kit requires a great deal of thought behind it. Each thing has to be planned out and when things are executed well and everyone's gameplay is executed well this class feels so satisfying to play.
Here is the hate part... when its not executed well or the party is dying all over the place in a fresh prog it feels like well your doing nothing.
A perfectly timed star almost turns me on it's so satisfying. And when you mis place and time it and the star pops before the damage registers you look stupid as hell. Then you are trying to scramble back with low GCD's heals that make you work super hard to correct your mistake.
When you have multiple AoE damage you can pop Horiscope before Aspected Helios then you have a 400 potency heal sitting on the shelf as a OGCD for 30 seconds. When executed well it feel so freaking good.
Collective Unconscious is hands down on of my favorite skills in the game. They way you can quick pop as damage goes out and give everyone a regen effect after is such a strong and fun skill.
But why I hate it...
In my opinion its OGCD kit doesn't quite keep up with everyone else's kit. It's a interesting kit that feels fun and satisfying but it's definitely not more powerful as the other classes. THen you combine that with the fact whm get's Bene plus Tetra. Assize is like Celestial only better with MP gain effect. Ast has serious mana issues why they couldn't give Celestial similar effects.
Then WHM's get cure 3. Like when things are bad everyone is dead you get this GCD broken as crap and save the day type of heal. When your a Ast your stuck lookings at your kit and trying to figure out how you can pump out that much emergency heals on the fly.
Then of course gravity not having stun, and celestial not having stun either.
I love this class but it needs some serious buffs or work. I hate that I love a class that is so much weaker then the other healer classes in nearly most every area. I hate that I refuse to play the other two cause I love this class and feel so handicapped at times.
Hopefully SE makes some good improvements come 5.2 and they make Ast great again.
P.S changes to the card system minus how clunky it feels during sleeve draw I actually like better now.
Give gravity a slow since tanks hate arm's length, give you a little mitigation while using AOE.
Ast is awkward in that it has to be worse at healing than the other two because of the cards and sects, but good enough to be viable healer.
Just SCH. Good scholars are best.
I max leveled AST to 80 already. It's a decent alt but my main healer is WHM for a reason. They crushed it in 5.0.