I get it. I do. At least I think I do, to some extent. Bear with me, I'm going somewhere with this (past the bold)-
When I see how Square has been making healer adjustments, I'm getting similar feelings as I had in 3.0 and 3.1. It's hard not to. For example:
We've gained MP economy in this expansion that's led to Cure 3 being much more usable overall, and I very much appreciate that, but Cure 3's "oomph" feels like less and less these days after the introduction of Earthly Star on a minute cooldown and Indom being buffed to 500 potency. It's lost strength relative to others' toolkits even though the spell itself has not changed one bit. Hell, it's lost strength relative to WHM technically simply by virtue of Cure and Cure 2 getting buffed while 3's potency was untouched.
Go back to ARR and the 550 potency boom of Cure 3 was something pretty much unmatched. It was limited in practical use for the MP cost, but the burst of it was very nice, especially in dual tank scenarios if you wanted to be very safe (And with an overcure proc, oh so sweet~). Now, while it's more spammable and that certainly comes into play, I haven't been in too many scenarios where I've though "Man thank god I have Cure 3 for this" outside of struggling groups in non-savage content. Others can get by without it, and it's still got a good bit of thought with its small radius that no one can see before its cast (unlike standing inside ground effects like ES or Asylum).
I see a spell that has had its own niche carved away a little more with each update. And if you get to fall back on Medica due to the range issues?
Your Largesse'd medica is doing less than a SCH's base succor, now. Feels good.
It's hard not to feel stingy and slighted about these sorts of things, and for me it always comes back to the same thing. Wanting to feel like you bring something the party really benefits from. I'm still not seeing it when it comes to the "raw, progression HPS" healer. I have great MP economy but it's not as if I've seen others struggling anywhere near WHM levels of the past, and that's probably due in part to refresh being as strong as it is from BRD and mana shifts readily available. There's nothing that really says "WHM power mode GO save all the things" either outside of cure 3 if people happen to be stacked for it. PoM is planned and often used with DPS since we're stone hurling machines now. You can say PI if it's also not on CD and there's life long enough to get 2-3 stacks, but it's really really hard to compete with the immediate stabilizing effects of an instant reactionary Indom; you are not encouraged to hit indom on cooldown like you are with assize, so while it might be unavailable, I find it's up to react with way more often.
Yet, as I've said and as others have said, things are probably the most balanced all in all that we've seen in a long time.
That doesn't mean I'm particularly happy. I have watched both shielding healers, Noct and SCH, get more abilities to keep up with Diurnal and WHM while keeping the benefits of shields - and make no mistake, shields are a massive benefit, especially in this game that is pretty much centered around burst damage.
Do you know what I really haven't seen?
Square designing in ways to showcase the benefits of HoTs. And that's what's really sad to me. HoTs often have two main benefits to them, and it feels like we only see one of them showcased.
One is raw strength/efficiency per cast, due to their slower HPS per-target and tendency to overheal. A lot. We see this - it's always encouraged to let HoTs tick people back up IF there's enough time between mechanics, and that requires coordination but it also leaves people in a danger state. There's a tradeoff, there, and you're trusting people not to screw up in the meantime while those HoTs do their job. Don't underestimate that extra danger, too - it's a real concern if people can screw up another mechanic and take an extra 15k.
That is NOT the only benefit of HoTs, though.
The other benefit is the one we rarely seem to see outside of auto attacks. HoTs can be cast in advance of damage over time, used to offset/buffer it since you have the GCD to spare now but might not later, and the tank doesn't need a 700 potency blast in the face yet. I can't understand why we haven't seen more damage like this to heal up, aside from people deciding it's not 'fun' damage to heal since it's sort of a maintenance healing. It's healing DURING the damage rather than "After the fact, let everyone tick back up."
There's also a third that ties in with the second (though shields do this as well). Simply put if you're about to be incapacitated, loading someone up on HoTs is a good way to increase their TTL, moreso than a shield if the HoTs get to actually tick for awhile.
We've got one ability in particular that really suffers from this. It's one of my favorite simple little abilities, too, but I also feel it ends up as something that feels underwhelming in a lot of practical use. Good ol Asylum.
Asylum has never been bad - but the reality is it's often used as a free extra tank HoT or as a desperate hope to get a couple of ticks in on people that are running around during other mechanics. Those times the raid is actually able to keep stacked, it's just a way to get out of casting another AoE heal, which is useful, sure. It's been a long time, though, since I got to use it in a way that felt fitting for a HoT zone. I very much remember being grabby-handed in A3S and dropping an Asylum ahead of time, conveniently where the entire raid was about to be while moderate damage would be going out - over time - letting the HoT ticks buffer TTL while I literally could not be casting anything else.
I'd really like to see things like this more often, where the HoT component is beneficial specifically because you cast it in advance and not just because it frees up another GCD for you to throw another stone. I'd love to have more of a reason to regen targets other than the main tank, OT, and that ranged who just HAS to stand 21 yalms away from you. Where are the DoTs that don't come from mechanic-failures and aren't better to dispel or ignore?
Want a mechanic that's better to HoT than just wait-and-heal-when-critical? DoT someone. Triggers an additional debuff if target goes below 70% hp. High desire to keep target topped off, best done with a HoT over less efficient shielding or spending more GCDs to continuously keep him above 70%. There. Now you're done with the only thing being "It's more healing over time if you have the time till the next raid-wham-o." I'd be glad I had a WHM or Diurnal in that case.
This isn't a new thing either, as we've seen mechanics in coil that were "Shield or suffer debuff" - we're just swinging the optimal way to deal with them the other direction while not preventing others to have a way to heal through it.
It's easy to feel a little annoyed when the game continues to be designed around surviving huge hits and (often) bursting them back up when you've got tools that could specifically be used in other ways, but never really are. I'm ultimately not satisfied with HoT design in FFXIV.
Edit: To add to this, there are some times where PI feels really great, and it's helping out in these cases of "I'm glad to have a WHM for this." I could still argue for tweaks to it in various ways to make it feel better or fit into more scenarios without overpowering it, but it's something that does get showcased, particularly when heavy movement is involved and more stuff is coming out NOW. I don't intend to say WHM is in a bad spot performance-wise. It's not. I do think there's a lot they could do to make it feel better, though.