Here are my ideas for each tarot card;
Balance - recovers HP of party to an equal percentage (the concept of balancing - the colour of blood being red)
Ewer - removes all negative status ailments (Water is aligned with Esuna/Leech - blue for the element of water)
Bole - HP regen over time and vulnerability down (the trunk of a tree - tree of life etc. - brown for nature and wood)
Spear - increases physical melee attack potency (spears are melee weapons - light blue, of the Ice element, for which Halone governs)
Arrow - increases physical ranged attack potency (bows are ranged weapons - green associated with woods, typical of bow wielders -coughgridania-)
Spire - increases magical attack potency (most mages live in towers or 'spires' - the bearded man (common depiction of a wise magus) is also present - purple associated with BLMs and arcane)
 
The Astrologian video also shows her using a Water element spell with a cast time of 3 seconds. There are a lot of speculation points I can make about that one cast.
- The only healer/support skills with a 3 second cast are Protect and Stoneskin, which are both of the Earth element. But it is not a 'support'/'buff' skill as;
- The aura is a healing/purifying aura. Heals and Esuna/Leech have the aura shown in the video, whereas buffing spells such as Protect have orbs surrounding the caster.
- The only known/speculated water-aligned skills are Esuna, Leech, Raise, Resurrection, Embrace and Whispering Dawn. Four are support aligned spells, whereas two are direct healing spells. However;
- The moment of effect of the spell produces the same sound effect as Physick and Cure. Yes, the two have the same sound effect, with a different animation however. This spell of the Astrologians has an obvious different animation with the stars in the afterglow, kind of similar to Adloquium with the shield effect.
 
- Stackable HoTs; think Hullbreaker second boss' Dropsy, except its a HoT. Weak burst, but very good sustain. Would definitely need to be balanced to make it viable.
- Delayed healing; apply a buff on target ally that expires after three->five seconds. When it expires, the heal is applied on target. Makes healing up hard hits like death sentence and ravensbeak easier.
- Delaying damage; apply buff on target ally in which they become invulnerable, so almost like a hallowed ground, except any damage and heal sustained during the duration of the buff will be applied when it expires.