Honestly, if it weren't for the "weak" damage (but that's mostly because AST lacks an AoE DoT and good burst attack vs SCH and WHM) of AST, I'd say it's utterly broken. Objectively, its healing potency is higher than a White Mage for Benefic II and Helios thanks to the persistent Sects (wait, why wouldn't you hold on to them?), powerful oGCD emergency heals (Essential Dignity and Earthly Star work wonders, especially with their lower Cooldowns versus White Mages (even with full Lillies, Tetragrammaton still only gets 48s as a cooldown and Plenary Indulgence not only doesn't benefit from Lillies but it also relies on buffs on party members to use properly (confessions)) and not being linked to your job's currency like Lustrate, Excog or Indom on Scholar.

Regarding that card debate, only two cards are really situational, but both of those can be used. Spear, Balance and Arrow are all of equal value now, with Spear boosting crits to be even more common (A Scholar would love you if you combo'd a Spear with their Chain Strat), Arrow making attacks all that much faster (Black Mages will love you for making their rotation more forgiving, and other classes won't mind the speed for the most part), Balance is flat damage (Which everyone loves). Bole is wonderful if you have it and need it, and is one of the better mitigation tools if you discount the randomness of getting it, and even Spire and Ewer have a good role in all parties (If you don't have melee DPS, give it to the tank(s) if they're getting low on TP. Use Bole on yourself or your co-healer if you don't have a RDM or SMN).

Having that "random" element to the Astrologian balances out its major strengths in healing and being good in support, I feel and removing the RNG would make it an auto-include at all times... not that it already isn't at times.