I think the healer situation is easily the worst role design decision in FFBE. This is where Gumi should really apply some of that GL exclusive magic. Ayaka nukes every other healer in the game from orbit completely. What I'm not sure on is how much of that is strictly needed to complete content, which is why I'm not saving for her.
I've seen much less talk about Ayaka's requirement than I'd like. Her power, yes, her convenience, sure, but her necessity, not so much.
I do think saving for her if you don't have Tilith seems like a sound plan. For what it's worth, going by JP schedule, even if next week is FFXI and Nier is a month and change out, I'm not sure Ayaka would release before it. They'd be very close by, in any case.
I think people who were bored of Ayaka being best healer have found success in using summoners in place of a healer.