I've only played SGE so far, but I'll put some of my thoughts in:

It has some really powerful healing tools. It's actually kinda silly. Holos is straight up better than its analogue in Fey's Blessing as Holos also provides a damage reduction. At this point, I'm surprised it also doesn't cost Addersgall because of how strong it is. Aetherial Manipulation on a healer is so much fun. I absolutely love it. The DPS is good, if basically the same as the other healers. However, I do have some complaints:

Phlegma's 45s charge time is awkward. It doesn't fit that cleanly into the 60s/120s burst windows that they want it to. I'd like it to either be 30s or 60s charge timer to fix this. 30s might be more fun, but I think 60s is more practical since your burst windows will be very bursty.

I don't have enough uses of Icarus. Sage is surprisingly about as mobile as BLM. It doesn't have Ruin II or Lightspeed to help with movement, and it really wants to turret as hard as it can because of Kardia procs. Toxicon is this, in theory, but, in actual practice, it's hard to do since Toxicon can only be granted through the breaking of E.Diagnosis. This is on top of only being able to store 3 uses of Toxicon. To top it all off, Toxicon is a DPS neutral at best and a loss at worse.

Another way to help with movement is if Dycrasia wasn't an AoE around me but rather an AoE around the target. It could act as both our main AoE tool and a Ruin II movement tool.

And, some personal opinions: Rizomata should grant Addersting. Toxicon II should be Toxicon I and a single-target version of Dosis that's equal to two casts of Dosis, while Toxicon I should be Eukrasian Toxicon which is the AoE and equal to two casts of Dykrasia.