Astrologian is first and foremost a healing class. Perhaps more so than any of the other FFXIV healing classes before it. What Astrologian lacks in damage dealing capability, though, it more than makes up for in healing prowess and versatility.
One important thing that is worth mentioning before we get into it: Astrologian benefits GREATLY from the Conjurer cross class skills. At the bare minimum, you’re probably going to want to get your Conjurer to 34 for Protect, Stoneskin, and Cleric Stance, if you plan on taking Astrologian seriously. Party members will definitely notice that they aren’t getting Protect and Stoneskin and your overall DPS will suffer without Cleric Stance.
Astrologian’s signature ability in Heavensward is Draw. Draw randomly picks one of six (beneficial) effects and applies them to a targeted party member. You then have 15 seconds to decide if you want to lock this buff in, or reassign it to someone else. The idea is you want to see which card was drawn and then reapply it to someone that gets the most out of that buff. For example, if you draw The Bole you’ll most likely be giving that to the tank since it reduces damage taken. If you draw The Ewer (MP Regen), throw it onto a partner healer, a caster DPS, or yourself.
Aside from Draw and its basic curing abilities (Benefic 1 and Benefic 2), Astrologian has a powerful instant cure ability by the way of Essential Dignity. Although this ability has a cooldown, it instantly cures without a cast time and heals for more potency the more damage the target has taken.
Lightspeed is your typical “oh sh!t” ability. Using it makes most spells nearly instant cast at the expense of some potency. Make sure to use that if you need to pop off some quick Benefics or Heloios (your AoE healing spell). You could also use it offensively to rapidly land some Malefics
Luminiferous Aether is an Astrologian’s best friend as it reduces your enmity generated AND refreshes your MP. Awesome! You newly earned ability, Diurnal Sect increases your attack speed and when used with certain actions that you’ll learn later on, adds an additional healing Regen effect. And of course, Astrologian has its own native status remover by way of Exalted Detriment.
And that just about does it as far as beginner Astrologian tips are concerned in FFXIV: Heavensward. As you level up, you’ll acquire new abilities that you’ll need to work into your rotation. But as long as you understand the basics, you’ll be in a great position to learn how to use these new abilities with ease!