I wanted a thematical reasonable way for each healer to shine in it's own way with their AoE piece to help out the party.
-White Mage's Holy makes sense because of the blinding light, making sense for it to stun enemies.
-Astrologian, with gravity the first thought would be "Heavy" which would mitigate damage in some instances but could create a big issue when it comes to pulling, so I would think a "Slow" effect would be more probable. not only is it a good mitigation tool like Arm's Length, but also gives the Astro time to focus on their unique piece, their cards.
Scholar, a lot of things wouldn't fit, like again looking at Heavy, it's too niche and would cause a lot more issues, so looking at Scholar's kit, a lot of it is mitigating damage output. So, the skill Art of War, creating a damage down, also makes sense.
-Finally, Sage, being the problem child and the best three debuffs taken, it doesn't leave a lot of wiggle room. however, the skills focus on their weapons, the laser beams could cause a paralyzing effect, keeping to the debuffs that don't directly deal damage. instead, i would think of more on a bleed effect, as Sage's kit directly despises any form of extra shielding or damage mitigation due to the nature of their shields.
this is just the healers as I've also seen people complain about Summoner, and I do enjoy the change. If anything I thought about how it could play similarly to other classes that have a "Three piece charge", such as new Monk and Recent iterations of Astrologian.
Currently Summoner has Phoenix and Bahamut, would be cool to have a third elder Primal so that Summoner could have
A-A-A = Phoenix (ease of access as Phoenix is primarily a support base)
A-B-A = Fill for a primal that could focus on AoE primary
A-B-C = Bahamut to maximize single target damage