I never said healing can't... heal, but no, healing is not mitigation. It does not mitigate anything. Healing increases HP until it hits its maximum. It therefore cannot increase maximum eHP against a single strike. If a boss tankbusters you for what would, prior to active mitigation, be 130% of your health, no amount amount of healing will save you. To survive it you must increase your maximum eHP, effective Health Points, e.g., by using mitigation, that which decreases the damage you take, effectively, increase your HP, or by increasing your maximum (and current) HP. Barriers can be equally considered as either a maximum and current HP increase (exempting old interactions like Stormblood Upheaval) or damage reduction. Healing, however, does not increase maximum eHP, unlike the likes of barriers, percentile mitigation, or max and current HP increases (Thrill of Battle). Healing heals; nothing more. You do not "stack" healing with mitigation (be they barriers, percentile mitigation, or ToB). You survive via mitigation and then you or your healers can decrease the gap between current and maximum HP as needed.
Percentile mitigation increases the eHP of your existing HP. It does not uniquely further increase the value of healing received over that time. It merely increases the length of time, because your existing HP takes longer to deplete, for which you are alive in which to be healed, including by your own healing. But so does a barrier.so the flat percentage is frequently applied to the HP regained as well
The only issue with the latter would be is if the barrier makes some (i.e., early) part of that healing excessive since it'd then do nothing. In practice, that does not happen unless you run into a fight with both incoming heals (Regen, AB, etc.) and a barrier pre-applied. That is far smaller vulnerability than the fact that the remainder of percentile mitigation can be wasted by death since the damage reduction is not as front-loaded (and therefore as immediate or sharply timeable) as on a barrier.
By that token, all defensives are useless unless they prevent death. No. The difference between a heal and a shield is that the barrier margin of a shield can extend maximum HP. If one has some 600 potency worth of healing until maximum HP, a 600-potency heal and a 300-potency-heal-300-potency-barrier will have the exact same effect (unless the 300p barrier can prevent a damage-dealing, directly or otherwise, debuff), but if there's only 300 potency of healing left to be done, the latter's eHP increase will be double that of the heal because the barrier can also increase the target's maximum eHP.To be clear, a heal that doesn't overheal and a shield that protect before damage are only distinguishable from eachother in terms of mitigation when the shield provided actually prevents death.
Redundant =/= weaker. TBN stacks with Galvanize and Eukrasian Diagnosis and unless taking extreme amounts of (pre-mitigation) damage over time, it is quite simply stronger than the combined mitigation and healing of Holy Shelltron or Heart of Corundum. Outside of your stat-buffs from job diversity, you do not need variety just for the sake of variety. TBN is stronger, stacks, and then has Oblation available atop that; the mere fact that other shields exist does not somehow make TBN defunct.Heals are only weaker because they happen after damage is taken rather than before, but there's not a single mechanic where a shield is necessary to survive it in the first place, so it's redundant, and even if it was necessary, we have SCH and SGE for it anyway.
It's not that complicated. For HoC to mitigate as much as TBN, it must absorb as much damage over its duration as 25% of the tank's HP minus what would be produced by 900 potency of self-healing under the tank's stats. Simple as that.This means in any sutuation that brought, as an example, Heart of Corrundum to the point the heal activates during the mitigation period and didn't outright kill the tank, then there is no situation where HoC alone didn't mitigate more than TBN even if you stacked it with Oblation.
Let's put it this way. Let's grab... the highest GNB parse we can, which happens to be on Zodiark. That tanks has 80008 HP, so let's just say 80k. If they were a DRK, their TBN would be 20k. On a top-parse GNB, Heart of Catharsis hits for around 8k. To equal TBN, then, he must absorb 12k damage within your 4-second 30% and/or 8-second 15% window.
That could be from mitigating half your HP (40k) damage (after other mitigation but prior to HoC) over the opening 4 seconds, or your entire health pool (80k) over the later 4 seconds, or some combination of the two (30k in the first 4 seconds + 20k in the later 4 seconds). Whatever.
Now, let's look at the actual outgoing damage from Zodiark Ex. Only once over his 9-minute fight, and despite never pairing it with anything more than Rampart, does his HoC absorb enough damage to make up for that missing 12k stat-based throughput. Once. (And that's not even accounting for TBN being able to pull off two-thirds more casts over time (in practice, around 55% more casts per minute, going by leading parses).)
Again, across a 10-minute fight, there was only one situation where HoC plus its heal absorbed as much as TBN, let alone TBN+Oblation. That's not exactly indicating a majority of contexts by which HoC blows TBN out of the water, despite HoC having a 67% longer CD than TBN and its trait being included in the same skill.
Unless undergeared, TBN is not particularly weak relative to competing skills, especially for its trait-equivalent being a separate ability. And it's certainly not weak just because "other barriers exist anyways."
Nor does any of that change that fact that, yes, TBN wholly scales with gear while HoC, Bloodwhetting, and Holy Shelltron instead scale largely with content (HoC primarily with content, the other two roughly equal under current damage intake). And no, you cannot just scale fully with both gear and content. The percent on percentile mitigation does not increase with your gear. (The only example we've ever had of that is the now long-defunct Foresight action from Marauder.)