Astrologian impossible to balance as it is

[Galdous]

If you are talking about pre buffs to astro then yes the astro is a support healer with weaker heals. If you are talking now the astro is support with stronger heals then both the white mage and scholar. The scholar is for now brought on more for its offensive abilities then just its pure mitigation. In Nocturnal stance the astrologian has stronger base heals counting the buff from the stance itself. If they would let astro nocturnal stance be a slightly weaker form of cleric stance without potency issues and reduction in mana cost to dps spells then I feel that would go a long way of letting the astro play the part of scholar.

[Ghishlain]

If you are talking about pre buffs to astro then yes the astro is a support healer with weaker heals. If you are talking now the astro is support with stronger heals then both the white mage and scholar. The scholar is for now brought on more for its offensive abilities then just its pure mitigation. In Nocturnal stance the astrologian has stronger base heals counting the buff from the stance itself. If they would let astro nocturnal stance be a slightly weaker form of cleric stance without potency issues and reduction in mana cost to dps spells then I feel that would go a long way of letting the astro play the part of scholar.

The problem is broader than what you're trying to make it out to be if you're trying to compare the AST kit to the SCH kit. I think Lyrica hit it fairly bang on in the head but I will add one point that pushes SCH healing to be much better / more efficient than AST heals - the Fairy. Fairy provides 4,000 potency healing every minute for absolutely 0 MP cost AND 0 GCDs consumed to the SCH . Noct AST has to spend a healthy amount of resources to perform a similar amount of healing (10 Benefics @ 10GCDs and 3,540MP).

In the end, any significant change to Noct will most likely happen in 4.0 when S-E can implement more tools to be used.

I'm wondering how overpowering it would be to allow sect changes in combat.

It wouldn't be too overpowered in my own opinion, but it wouldn't serve too much incentive to do so either. There would be no reason to Sect Swap when party with a SCH since you don't want to risk overriding Deployed Adlo / Crit Adlo. Double hot + a shield would have some applicable use in WHM/AST compositions and probably make it a bit more desirable but it's hard to fill the niche that SCH currently has in the current meta iteration so this composition will be unlikely to occur.