As I saw somebody post before, "I'd rather have a 35 potency per tick Bio and a 35 potency per tick Miasma than a 70 potency per tick Biolysis"
I honestly think people would pick what they think is most engaging for them. Whether people will choose a particular healer in a party setup will mostly boil down to balance.
Healer difficulty would be affected by the complexity of the job and that can be either in the heals, in the DPS or both. And we already had this.
In 2.0 WHM was the "easy" healer, its heals were simple, its DPS was simple, it was easier to pick up.
In 2.0 SCH was harder because it was more technical because on the healing side you had to be more proactive and it felt more tactical, which is one of the job aesthetics and you had a lot more in your DPS kit.
And it worked.
AST got added to the mix, which was where we ran into balance problems because AST has to fit both SCH and WHM's roles in the party and SCH got buffed and it became OP.
But AST had its complexity. And it is STILL more complex than SCH or WHM and that's why I play it over SCH or WHM despite being a former SCH main.
And SGE has a 2 button press to do skills SCH/WHM/AST only have 1 button press for because of the Eukrasia mechanic.
IMHO with 4 healers and a split between 2 types of healers, I think they are in a much better position of offer different levels of difficulty and variety whilst maintaining balance. And I get the feeling this is what their vision sort of is, but are still holding back from doing what's needed to achieve it and it seems that's because of accessibility. I think they want to keep all healers accessible. I think they can achieve this and maintain accessibility by putting the complexity and difficulty spikes in the DPS kits and increase healing intensity on content where it matters without killing accessibility. You solve a lot of problems doing this.