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

[Kaethra]

The Diabolos Hollow fight in Dun Scaith uses several mechanics to put a definite focus on survival over dps. DpS is good but surviving the fight is more important.

I saw a Tank get one-shot last night in an extreme because they used a cooldown at the wrong time. Thought a tank buster was an AOE. A simple mistake that a veteran player can make if they haven't done a fight in a minute. But a mistake that dropped him to the floor. That was in the easier extreme, Lakshmi. We recovered, but it served to get everyone's attention.

These mechanics everyone is asking for exist:

Lakshmi Extreme
Susanoo Extreme
Shinryu Extreme
Deltascape Savage, all four versions.
and I assume Ultimate Coil has it too.

Do that content, people. As someone else said, Expert Roulette is not the endgame.