The difference between the "3 different types" of DPS is enough that Stormblood introduced two DPS jobs with wildly different roles, and no tanks or healers.
And no, you didn't "moan we didn't get a 4th healer this time around," but you literally complain in the same post "they didn't add a 4th healer because of balance concerns." You're trying to have it both ways, mate.
To be clear: the point I'm trying to make is that their justification for not adding Chemist back when they originally planned in HW is not the same as their justification for not adding "a healer" in ShB, nor does it mean when the planning phase for the next expansion comes around, that the same justification for not implementing a healer will hold indefinitely.
Yoshi literally stated that one of the reasons they implemented DNC as a ranged DPS was because of the lack of options for ranged jobs compared to other roles. Well, we have 4 tanks and 4 melee now, so if the same reasoning holds then next expansion is due for another caster, healer, and/or ranger -- and we just got a ranged job.
I'm simply stating that based on the precedent, unless they've come up with very new ideas for the same job since then, I find it very unlikely that the next healer will specifically be Chemist.
Couple points here:
1. While I admit I'm having trouble finding the actual interview(s) that are more specific in backing it up, both TV Tropes and the FF Wiki state,
Originally Posted by TV Tropes (FFXIV Trivia, 'Lying Creator')
2. I think you're wildly overstating the point with "doing content with your roles rather than new jobs". In this case, the intent is for every healer to have the same base ability and tools needed to complete raid content, even if not the same ability to parse in FF Logs. "Adding new jobs to fix balance issues" is a stretch for the current design, as while Gunbreaker verged on that with regards to Yoshi-P previously stating an intent to add a new off-tank to balance the tank roles out, GNB instead became an opportunity to rebalance all of the existing tanks to fulfill all tasks equally. I personally expect that a new healer could potentially lead to similar re-examination of existing healer jobs.Originally Posted by Final Fantasy Wiki (FFXIV Astrologian, 'Trivia')
... I just don't think a job based entirely off of instant healing and minimal spellcasting is going to bring that examination about.
I'd been discussing with a friend some time ago that apparently some datamined info back in 1.0 hinted that the broad elemental abilities given to Conjurer were intended to be a gateway into introducing Geomancer as an alternate branch off it at a later point, had Scholar's implementation not soured the devs to the idea of branching jobs. Not that a lot of information still persists from back then to back his claims, although the existing principle seems sound enough.