S
Sofia is a strong, healing, and supportive character. Her passive gives her +10 HP when she heals an ally with magic, and this increases by +2 range at higher levels. A good thing about Sofia is that she is available in Theodora’s Path for basically free, and it isn’t much of a grind on the other paths either. You don't need to invest much in Sofia, and she is good without much gear. She can also work as a mage tank, but her HP growth isn’t very high.
A
Ultand is available in all of the character Pathways. Her passive is similar to other characters, but her passive gives her heal to adjacent allies. When she has this at level 35, she will also grant dodge to her allies. Overall, these passives are good and provide healing and prevent her carries from getting one-shot. Sadly, she lacks Physique, which is the reason she isn’t an S-tier pick. Ultand has good growth in terms of defence, resist and HP, which allows her to be a little bit more of a frontline healer.
Fianna is an RNG healer. When healing an ally with magic, she will sometimes reduce the magic cost to 0. As she levels, she can also heal her allies and restore additional health. Unlike stable characters like Sofia, she is based on luck. You can get Fianna's luck quite high in the healing class, especially with the +10 healing item coming from 
Ludia. She has 55 magic growth, but very low HP growth and speed. Ideally, she can be a healer in the backline.
Mage DPS / Sub Healer
Olympia is available in all of the pathways. The crit and her sustain with magic thanks to Ardent Nosferatu is extremely strong, especially at level 35. It makes Olympia constantly crit the enemy! She has 50 magic growth with 35 speed and 35 dexterity. What makes her so strong is the White Magic Spell with Physic and Heal. She has lots of good spells!
Bonaventure has a preference for White Magic Skill alongside some other strong abilities. He has good magic growth at 45, and good dexterity at 50. Across the board, he has some good stats to be a mage DPS. Unfortunately, he doesn’t have Physic, but he does have Heal and Recover, which are a good combination to have.
Fabio has 50 magic growth and can also be a sub-healer if you need bonus healing. He doesn’t have Physic, which means he can't be a full healer and is better as a DPS character.
Healer + Buffer
Leda is the best buffer in the game. She can give +7 resistance, +7 defence, +7 damage, and she can be next to characters that give extra turns, stats, and more.
Tialla doesn’t have the best passive in the game, but she does have some decent stat growth. She has 45 magic, 40 dexterity, 35 speed and 30 HP. She has a variety of Lend abilities that buff her teammates' stats, including range. This could be good when you want to over-buff an ally so they can get extra stats.
Dante's passive ability lets him give nearby allies additional dodge. This gets even better if you stack him with stage direction, as you can turn him into an aura bot! You need a lot of charisma to get this to work, so you need a class with high charisma to go with it.
Sha Lan might seem a little weaker than some other healers, and in some ways that is true. Her Passive can provide assist magic, and when it reaches level 35, it also gives adjacent allies extra speed. In the backline, she can provide many buffs to nearby characters. Train her as a backline. She has high dexterity, magic, and speed but not the best HP, so she can be a mage DPS but not the best either.
Alternative
Sirocco has 40 magic, 45 speed, 50 dexterity and is overall a very even character. Sirocco has a preference for White Magic, and our expert uses him as a healer in the frontline as Sirocco can become very tanky. They do not have physique, but they do have recover, restore, fortify and warp. Warp with Sirocco is quite good.
Ninae can easily go into Bishop. Her passive is very good and makes her even tankier. At level 35, she can even pass these stats on to allies within 2 spaces. She has good defence growth, and 35 magic. She has decent overall stats for a tanky frontline character. She could even be a healer, despite her low magic gain.
Class Preferences
Priest is the first class option. Priest is great for White Magic, and it gives 10 magic, 5 speed, 5 dexterity and 5 HP growth.
Shaman has 15 magic, 10 speed, 10 dexterity and 5 HP growth. For healers, Shaman is a good choice because it gives you extra offensive growth if you want your healers to deal damage. Not having double White Magic isn’t a big deal in most cases, and these extra stats could help.
Ovata is a choice for damage dealers. It has high magic, decent speed, HP and dexterity. It could be a good early option before switching to Bishop later on.
Bishop is a natural healer class. It has double White Magic usage, which is incredibly good. The unlocked ability grants resistance to +3 adjacent allies, which can be really strong. It is good on frontliners.
Caladrius excels in the Black Magic class. It has decent mobility, 10 magic, 5 speed and 10 HP growth. I wouldn’t change into this class for stack gain unless you want health. The Master Ability that provides movement speed is nice, but it's more utility-focused.
Troubadour uses both White and Black Magic. It has decent magic gain, HP gain, etc. The Master Ability, Songs of Courage, lets you stack it on multiple healers at once.
