1): - Benefic II + Aspected Benefic is 2 global cooldowns, not one. In a unfavorable comparison (Scholar uses Adlo -> Lustrate -> Lustrate, but not a second Adlo, is not under the effect of Dispersion or Fey Illumination, and Eos does not heal the same target.), Scholar's 1800 potency loses out to Astrologian's 1901 (312.5 + 125 + 406.25 + 1058). With Dispersion alone, Scholar pulls back ahead (1920 vs 1901).

For a single-GCD comparison, though? Synastry Benefic 2 is 630 potency, modified to 756 by +20% healing.. increased by 40% to 1058 on the single Synastry target. Which has to be in your party. This is less than the 600+600 (1200) Adloquium + Lustrate provides in the same global cooldown. This can additionally be used across multiple targets, or on targets not in your group, both of which are very relevant to triage healing.

2) You have (at best) 9 instantly accessible Aetherflow charges. It is not difficult to roll into important fights with 6 (Aetherflow + Dispersion), and many times you can easily hit 9 or 12 in a prolonged fight. Using one on Indomitability is a direct improvement to Lustrate, because it is healing for more raw health among affected players, such that it is almost always correct to use Indomitability even when triage healing your own group. Shielding vs Healing isn't really a choice, either - unless you're trying to heal a DRK with Living Dead up, shields are significantly better than heals on focused targets in all but the most stringent edge cases.

Additionally, you seem to be ignoring Astrologian's hard limit on casts - it can cast one spell every global cooldown, with only two exceptions to this rule - ED and Retrogradation. Scholar is not tightly bound to this rule when its cooldowns are active, allowing it to get off as many as three heals in the same global cooldown even without Eos. This allows it to match even White Mage in short bursts - Indom + Swiftcast Succor + Lustrate on a focused target is something that Astrologian has absolutely no analogue to, and White Mage needs Cure III to see a similar single-GCD effect.

3) Cards are and have always been RNG. Balance is fantastic, as always, but it's also the only one of those cards which affects burst in any way. Now, Astrologian's offensive utility is better than Scholar's, but you didn't even think to mention that - Celestial Opposition and Stella are both fantastic tools compared to Scholar's native options, and most of Astrologian's cards have some sort of useful impact in battle - but only Balance actually provides burst pressure in itself.

It is absolutely true, however, that using Energy Drain reduces your healing throughput - but it can be worth the loss of Lustrate to remove an enemy AST or WHM from the fight! It's one of the few options in Scholar's toolkit - Scholar has the weakest native toolbox of the three healers by far, and I will never argue that point.

4) No. Retrogradation is a slightly souped-up combination of Assize and Fey Caress, whose unique trait is sometimes removing an important buff from someone close to you. How often do you actually remove a key buff from someone with it? Because I get knockdown value out of Aura Blast in easily 80% of my matches. Retro is probably actually the worst of the 3 healer special abilities - White Mage would barely function against melee without Sacred Prism.

But hey, what do I know? Maybe i'm just getting carried by Astrologians.