Astrologians is simply the weakest healer in a Feast environment.
WHM have Protect to reduce damage, Divine Bene to shield, Assize is an AoE heal and Benediction for full target heal - also with the help of Lillies to reduce cooldown period on all of these skills. Plus a Regen.
SCH has a 30 second minimum cooldown on Aetherflow - because when you use skills that use Aetherflow your Aetherflow cooldown goes down by 5 seconds. If you use Broil, you gain an aetherflow stack and when you use that stack your Aetherflow (skill) cooldown goes down even more, so essentially you have tons of instant cast heals.. plus Adlo spam + Aura Blast, great to get people off you.
Astrologian has Benefic, Benefic 2 and Essential Dignity for heals, has to rely on cards to benefit party.. you have the instant cast proc on Benefic cast + Lightspeed which is good but it is really not able to heal a focused target as well as the other two. Deorbit is pretty situational too, you have absolutely nothing to protect you if you get focused except trying to kite the enemy.