Why is Colphne so undersold?

I've been playing since mid-December. (And just for reference, I'm at lvl. 60, T8 boss, but not highest reward level, haven't seriously attempted Crossroad Challenges yet, and only played Frontline Gunsmoke Decisive Battle on the last day.) Unless I'm trying to drilldown a boss, I usually bring Suomi or V6 Colphne because they do a good job restoring stability index. (And if you see this within the next 3 hours and 45 minutes, and don't have Suomi, roll for her now.)

With Colphne, I can spam heals with no cooldown or confectance cost using L2 Crisis Aid. (You can skip ahead if you already know what it does.)But it gives at least one stability index--and if a character's stability is broken, it restores 2 more stability index with L6 Curva and with her one-turn cooldown passive, restore 4 more stability index. And with her Doctor's Orders fixed key, it applies Shelter, to reduce incoming stability damage by 2, for one turn.

And again, this is on a skill I can spam, with no cooldown or confectance cost. (In fact, you gain a confectance point for using this, that you can put towards her ult, another amazing heal.)

I get that her damage numbers/skills are really not good, but at least she gets one support attack that deals 3 stability damage (and could trigger V3 QJ, then Sharkry.)

I have a V6 Ksenia and Cheeta, and I know Centaureissi is coming up--but from my experience with the first two, I've run into problems managing low/broken stability, and neither seem like they do much to help with that, and it doesn't seem like Centaureissi does either (but maybe I'm misunderstanding something with her kit.)

But really, I'm trying to understand why many players undersell Colphne, despite being the best healer in the game--particularly when it comes to maintaining stability index (or if I'm possibly misplaying the other healers?)