I hate to, but I think I put down healing for now. Please make it engaging again, SE.

[GrimGale]

The nature of healing in general is that you don't heal when you don't have to. The nature of scripted encounters is that they're very predictable in terms of healing.

And for good reason. If we take the tether pairs in Titania as an example - they target dps - nondps pairs. So you simply send dps north and nondps south to trivialize it. Now imagine if the pairs were truly random and you had to look around carefully and adjust every time. This change alone would halve the encounter clear rate. We may not care about this, but SE does.

Designing encounters is a whole lot more difficult than this forum would have you believe.

The encounters are designed in a way to prevent players from catching up to their mistakes. A huge chunk of the mechanics involve instant death in some way. That's what makes encounters complicated. The problem is no amount of healing can solve those prevalent mechanics nor is it meant to. The mistake is bound to either kill the player or simply kill the party. So from time to time SE puts some scripted "heal checks" where healers need to keep the party from dying from unavoidable damage.

Those moments are an exception rather than a rule.

[LariaKirin]

The encounters are designed in a way to prevent players from catching up to their mistakes. A huge chunk of the mechanics involve instant death in some way. That's what makes encounters complicated. The problem is no amount of healing can solve those prevalent mechanics nor is it meant to. The mistake is bound to either kill the player or simply kill the party. So from time to time SE puts some scripted "heal checks" where healers need to keep the party from dying from unavoidable damage.

Those moments are an exception rather than a rule.

What is a "heal check"?

[Mansion]

What is a "heal check"?

A given output of damage in a reduced time frame. Meaning it checks that party members have been healed in between.
The one I remember best is Kefka where it would bring HP to 1, make people unable, an only give a few seconds to top people up before a raid wide.
White hole in ExDeath is arguably a heal check too, you had to Max everyone quickly, after a mechanic where people were running around.
Maybe the adds you had to heal to full during Shinryu Ext too.

I don't see strict healing checks in Eden, more like continued healing requirements... maybe the flares into share on Voidwalker... I haven't tried Titan though.

[Crushnight]

A given output of damage in a reduced time frame. Meaning it checks that party members have been healed in between.
The one I remember best is Kefka where it would bring HP to 1, make people unable, an only give a few seconds to top people up before a raid wide.
White hole in ExDeath is arguably a heal check too, you had to Max everyone quickly, after a mechanic where people were running around.
Maybe the adds you had to heal to full during Shinryu Ext too.

I don't see strict healing checks in Eden, more like continued healing requirements... maybe the flares into share on Voidwalker... I haven't tried Titan though.

Titan's heal check is right at the end with his spamming Tumults spam, voice of the land, Tumult spam, voice of the land, Tumult spam, voice of the land, enrage, but all this could be bypassed if have high enough dps in group to kill before that part.

[LariaKirin]

A given output of damage in a reduced time frame. Meaning it checks that party members have been healed in between.
The one I remember best is Kefka where it would bring HP to 1, make people unable, an only give a few seconds to top people up before a raid wide.
White hole in ExDeath is arguably a heal check too, you had to Max everyone quickly, after a mechanic where people were running around.
Maybe the adds you had to heal to full during Shinryu Ext too.

I don't see strict healing checks in Eden, more like continued healing requirements... maybe the flares into share on Voidwalker... I haven't tried Titan though.

How much damage is a given output of damage?
What is the time frame? 4 seconds? 5 seconds? 6 seconds?
At what point does this stop being completely arbitrary?

[Mansion]

At what point does this stop being completely arbitrary?

You got it : it doesn't. One could argue that it's just... healing. Just like a DPS check is just... DPS.
I don't know if you could consider gear gating too, as some very specific raid damage hit higher than HP pools so you simply need shields (Morn Afah, O12S enrage?) and mitigation.

Regardless of all of this, it boils down to "not letting people die", with some moment more intense than some other.