How can tanking and healing be made more broadly useful in more "role-specific" ways?

[Shurrikhan]

Lack of triage and the absurdly high healing potencies play a huge factor into why healers have so little engagement with their actual role. When you can set up at 10k regen tick, it crosses far into ridiculous categories. Likewise, the predictability of fights impacts them both. Nothing can truly be addressed until the devs embrace less scripted, high triage based fight design. I'll go one better and argue tank immunities are also part of the issue. I suspect their intent had been for emergency use, but we don't run content like that. All immunities have become is removing an annoying mechanic from the fight. Unfortunately, I can't say how well received high triage would be, especially at the lower levels. On the one hand, it would go a long way in forcing players to actually improve at their main role. On the other, well, whenever I let my co-healer solo in DF they tend to panic.

By "triage" here, do you mean something like staving or cautionary heals (i.e. for an incoming damage of unknown proximity or strength), as opposed to known requirements or exacted heals, or is it just being used as another word for healing? (Just trying to be sure before I tally the idea.)

Problem: Healers and tanks having little reason to go out of their regularly scheduled heals/mitigation skills, as the ratio of DPS to healing/mitigation is more important.
Solution: Make having high health more important.
Explanation: With decrease in HP, comes decrease in damage output. The character gets held back by wounds and the like. Keeping a tank at 50% could cut its damage by 40%, for example, even more at lower levels than that, so "brute-forcing" their way through avoidable attacks would not be a good idea for tanks, while healers doing heavy DPS while keeping the party at low HP until a scripted "nuke" comes would be a horrid idea, as well.

So like a raid-wide Atrophy (or, Reverse Vigor) mechanic? While as a gimmick that'd do little for healing or tanking, that would definitely be interesting to see some time. I just worry that it would change little in the aspects of "maintain HoTs / ensure Fairy's existance; DPS between".