Priest and Priestess have pretty good access to healing and some big creatures to guard them with. Not sure they need much armor when they can use a single quick action and 9 mana to heal like several rounds worth of damage. They have x1 access to burst healing for a reason you know, and burst healing actually is quite mana/action efficient, unlike attack spells contrary to popular belief. Healing always gets past armor, a minor heal is 5 dice healing for 5 mana and a heal is 8 dice healing for 9 mana, and if your opponent takes around let's say four actions and 12 mana to get maybe 10 or 15 damage on you, cast a heal for a single quick action and 9 mana and it could all be gone, just like that.
Holy attack spells have better chance of daze and stun combined than lightning does. The main purpose of holy attack spells is to daze/stun, as well as provide burns in the case of malakai priest.
If she does end up with a more powerful holy attack spell, I'm thinking that it will be another low dice attack spell with a high chance of stunning the enemy. A high stun chance might be a pretty good finisher for a holy mage now that I think of it.
Something that would be really awesome would be an incantation spell that gives a creature +6 life and stuns them. Maybe it would be called something like "Asyra's Judgement". If cast on a mage, it helps them when they are winning and hurts them when they're losing. Kinda like the holy school's answer to drain life, drain soul and drain power. I would love to see something like that.