With A1S cleared and working on A2S as a WHM, I'm amazed at players doing this as Astrologian. It's obviously possible to clear the content that way, but I imagine the overall stress is higher. So far I've only run AST in EX primals and normal Alexander.

As I've understood it the highest possible iL at the moment of this writing is 186. Assuming that the fight is tuned for 190-200 it's a possible, but strenuous task to tackle the content right now. Unless all players in the party are performing exceptionally well the healers need to help out in order to meet the DPS check. Perhaps even with that exceptional performance, healers will need to help with DPS. That's how we did it at least. Our SCH was in Cleric Stance quite a bit whilst I healed solo for various parts.

As a WHM pushing out that kind of healing across the group wasn't too hard (much due to DS and/or PoM), but mana-intensive. Between the Gunnery Pods, Hydrothermic Missiles and tank-busters there's a lot of damage to take care of. If someone falls it would eat up a large chunk of mana or even more importantly - a large chunk of the much needed DPS.

I'm a firm believer that Astrologians shouldn't be able to flat-out match a WHM in pure healing, or a SCH in shields and mitigation. That is the identity of of the WHM or the SCH. Encroaching on that identity would invalidate the usefulness of the job in question (i.e. why even have X?). The Astrologian must have its own identity. At the same time, the Astrologian must be able to reach the same end result (not necessarily through healing or mitigation) with the available tools without a too significant difference in cost or effort.

This brings me to the cards and the utility toolkit of the Astrologian. My impression is that they're not strong enough or reliable enough in empowering the group to replace whatever you'd lose from not bringing a SCH or WHM in progression content. How big a part gear and number scaling play in this I don't dare comment on.
  • Lightspeed is now again useful for healing. The Lightspeed Trait however is basically useless as the ability would practically never be used to deal damage. In a DPS situation trading 25% resource cost for 25% damage dealt is nonsensical.
  • Luminiferous Aether is a good ability to have, but since it's the only reliable source of mana management there needs to be some other way (trait, proc, combo effect etc.) to manage mana.
  • Synastry is walking the line. For the size of the cooldown, the effect appears to be too weak. If Synastry worked on AoE healing, or copied the spell effect or had a longer duration I'd agree more with a long cooldown.
  • Collective Unconscious has very limited use despite the potency-buff in Diurnal. For both sects the crux of the matter is the fact that the Astrologian cannot act or move whilst channeling. For Nocturnal there's the additional trouble of placing the Astrologian in danger if the mitigation shield is needed for other party members but not the Astrologian herself. Conceptually I like the idea of CU simply affecting all party members with a massive range. Balance and number-wise I have no idea how you'd balance it.
  • Celestial Opposition feels like a mess of an ability. In a raid environment the biggest use is the buff elongation since most enemies will be immune to stun. But the stun effect is probably the reason his ability has a high cooldown. If the ability is meant for killing things more efficiently, why's the valuable buff elongation bundled with it and gated behind such a hefty cooldown?

As for the cards, they are conceptually very cool (reading the random future and guiding allies with buffs). But in progression I believe reliable and reproducible methods are much preferred. Right now the cards feel too weak to offset the price in healing power and mitigation the Astrologian had to pay for the deck. If the cards are made too strong, they'd just trivialise certain content. If the cooldown is too long, they'd lose even more reliability and it really doesn't feel like the game's framework can support a more complex card system. Whatever solution crops up, I'm curious.