To clarify somewhat on this point since I brought up the concept of Heal Absorbs (or Aetherblight, as I'd call it here), it can be boring on its own, but it is also a very good design element to mix into a collection of simultaneous mechanics. Let me explain an example from a dungeon in the new WOW expansion (using Mythic 0's version of the mechanics):
- Every 20-25ish seconds, someone is marked with a hefty DOT (which also reduces movement speed, making it harder to dodge other mechanics). The DOT can be cleansed with the WOW version of Esuna, and has an infinite duration, it lasts until cleansed.
- Upon cleansing this DOT, everyone who didn't have the DOT will be given 1.2m (for context, my best geared healer has about 5m HP) of Heal Absorb. While any HA remains, the player also takes 100k damage per second. In M+, these numbers scale up as the key's difficulty scales.
- At 50% and 0.1%, the boss consumes the entire battlefield space (an airship deck) with shadow, instantly killing anyone who didn't mount up to fly away to dodge the blast. While mounted, you can't heal, and so if there's any HA left, the DOT might end up killing your team, meaning that fast cleansing of the HA is paramount
On its own, 'heal hard' is not necessarily 'interesting'. It's what it allows for (designwise), when combined with other mechanics, that makes it interesting. That, combined with the fact that in WOW, we have a LOT less access to AOE healing. We don't have Medica, or Succor, or Cure3. The healing combo I would use to handle something like the above mechanic, on the healer I main, requires 4 different buttons, with CDs of 10s, 10s, 20s and 30s respectively. If I don't have one of those buttons up (eg the 30s CD hasn't come back yet), then I am required to 'improvise' to fill that gap, something that we don't really have here in FFXIV because we always have Medica/Succor etc to fall back on as a 'last resort'. Our 'challenge' is derived from 'how do I heal this while losing the least amount of damage?', but over there, 'how do I heal this' can sometimes be the whole question
Also, on the subject of UA, 'when this debuff is dispelled, it does damage to the raid' is something I've seen in a fair few raids in WOW, and it'd be nice to see it here, but the devs tend to instead swap the 'dispel method' from casting Esuna (giving Healers full control over 'pop speed'), to 'everyone has to 'pop' their thing by doing some movement thing' (eg break thorn tethers in P4S Curtain Call, stand on fuses in M3S, etc).
Here's a random funny idea I just had while writing this: A mechanic in a raid fight that works like Allagan Rot. It hits 0, you all die. The way to pass the Rot though, is by casting Esuna on the player with it, at which point it jumps to the closest player in proximity. Throw a 'you cannot receive Rot again or you instantly die' debuff on someone for a bit once they're cleansed (so you don't just juggle it back and forth between two players, eg the tanks), there you go, new raid mechanic
SGE's ability names are based on the Four Humours theory of medicine, but A: it's names only, and B: they prioritized 'sounds cool' over 'has thematic sense'. Which is why we have Addersgall gauge (named after Gall Bladder Bile) that is spent on several moves (-Chole, the other bile (I forget which is black and which is yellow)), Haima (blood) as an OGCD that applies a load of layers of shields, and Phlegma (wonder what this one refers to) as 'it does damage'. If we were prioritizing theming, maybe we'd have some system wherein we have 4 gauges, referring to the four humours, and each is spent on their own spender (eg the Blood Humour gauge is spent on Haima/Panhaima, rather than them being 2min CDs). But hey, SGE is such a blank canvas (due to being such a clear copy of SCH for the majority of its actions) that I'm sure we all have our own ideas on what could be added to SGE to give it a design direction of its own (personally, I'd heavily expand Kardia's role in the gameplay)