"Ruach" is a name I've held onto for a while for White Mage, as with "Ablution." Something I've thought since Shadowbringers was that rather than replacing the earth/wind/water-but-not-actually trinity with raw light magic, that they should've been a combination of light and earth, light and wind, light and water (if we ever actually had a water spell). So instead of "Glare," we could have "Sepulchre." Instead of "Dia," we could have "Ruach." Instead of (HA you wish), we'd have "Ablution."
And to clarify on your and the other questions in relation to Banish and Ablution, yeah, Shurrikhan has it correct that the choice between the two is one has no MP cost while the other restores HP. The thought was since you do need to use it semi-regularly, you'd have the option to address healing needs while still working toward your Retribution and keeping the cooldown running. I imagine the second cast would just be the free CD and you'd have to spend the MP on Ablution each time if you used it twice, though having the second cast be free could be interesting; however, then it's sort of a situation of "Why wouldn't you?" Unless the party is at literal full HP, it's free healing. Something else I'm thinking more about in hindsight is it would probably feel better for these double cast actions to have fast GCDs like with Ogi Namikiri. That would mess with the numbers I've set up currently, but could easily be adjusted for if this if the concept got picked up.
Generally, new jobs and job reworks very likely begin in a similar state to this. The point is to establish ideas, then see what the rest of the team gravitates toward before finessing it into something polished for release. I can't speak to SE's design process or anything, but you always want to start with rough drafts. It's also very likely that jobs start out as very OP at first and are then gradually tuned down until you hit where you think is the right sweet spot. So yeah, this is really just a proof of concept.
As far as the concern of it still being a debuff and thus still requiring the player look at the target's state, I do have a solution to that. It's a realm of UI that I think is painfully unexplored in FFXIV, which is to superimpose effects over enemies. Here's an example from Genshin:
In the above image, that character can inflict a special condition on enemies called Riptide when he lands critical hits on them, and that watery reticle effect is how you can identify what enemies are afflicted with Riptide. But we could also use the ground underneath enemies as well such as in this League example:
We could be using a boss' target ring to communicate information as well. We already do so with general information. Imagine if Dia created 4 pizza slices within the the target's hitbox, perhaps using ground visual effects similar to what you might see in some of Innocence's mechanics (though not the same to avoid confusion in that fight), like the rainbow glittering floor. And the thing is, one concern that may come up would be that kind of UI getting too confusing if multiple jobs use it and multiple players are afflicting those conditions at once to the same enemy. Could you imagine alliance raids? But we already have a solution to that in the game, which is having effects that only you can see. Consider that in P11, you can only see whether you are being targeted for light or dark mechanics, but you can't see anyone else. If you integrate that same concept, then you'd only ever see your own UI, and no one else would see yours.
I'd say in general, we should only have 1 or maybe 2 of those per job (depending on how the two interact if you have more than 1), but it's a way that could make something like Dia very easy to identify without needing to always keep track of the boss. But what I think is nice about this Dia concept is the timing of when you apply it isn't strict, which was the main thing I was trying to go for. That said, I do also respect your criticism of it feeling obligatory, and it's definitely something that could be reimagined in some capacity.
Something that comes to mind actually... The idea for the level 4 Retribution system came from this character that just got released in Genshin, Freminet. His skill creates a pressure gauge where each stack raises the pressure 1 level. At level 0, reactivating his skill has him perform a Cryo attack (ice), and reactivating it at max pressure has the attack be purely physical, where reactivating it somewhere in between does a mixture of cryo and physical. I'll share a timestamp that showcases what this looks like visually: https://youtu.be/eYgUbuYzDos?si=GqrGjKo4jE3FgRsW&t=45
Maybe Dia is something that has a cooldown with charges, and the effect changes depending on your Retribution level. It's just difficult to consider what those effects can be because if any of that has to do with damage dealt, then whatever deals the most damage is what you'll do 95% of the time.