Please talk with the design team and tell them that her primary problem is that she is both the premier defender/staler AND healer in the game. That doesn't mean there has to be another heal character, it just means one of her healing abilities (hint: HER ULTIMATE) has to be reworked. Have you guys ever considered giving her an ultimate where instead of reviving, she gives a single character a sort of protection where they can carry over all of their abilities, shield and weapons on to the next round? As in, the main Op'er on your team dies, but they had the protection ulti casted on them, so on the next round the respawn with everything they had, saving their economy basically. This could be very strategic and would still make sage the go-to support character, plus she would still have her heal.
We're not currently talking about full ability reworks like that, and would like to avoid that if possible. I agree with your points around stall + heal uniqueness on Sage being an issue due to lack of choice competition - I spoke to that a little bit in another one of my replies here. We want to approach this methodically so we can shave off power in the right areas, but want to avoid full reworks like that if we can!