why every FF14 healer is berserk healer

[Reinhardt_Azureheim]

Sounds like raidwide mitigation isn't something that should be every role's responsibility.

Kind of...? I mean mitigation in a vacuum isn't a problem, it's only becoming an issue if you can efficiently align tank & dps raidwide mitigation if it effectively has no gaps + the incoming damage is too infrequent and coordinated in bursts.

Same also applies to tank damage taken and kitchen sinking being something you can do due to how busters are spaced.

Realistically it would take the following to make healing requirements go up to warrant healer presence more:

• Tank busters (occasionally with DOTs too) being thrown more regularly and as part of raidwide damage (see Emerald Weapon EX p2 buster) or part of mechanics (see Neo-Exdeath "Delta Attack", Eden Prime savage "Delta Attack" inverted, Eden Leviathan savage "Black Smokers", DSR p6 "Wyrm's Breath" and many more).
• Raidwide damage and/or regular tank damage being much more frequent and also uninterrupted and less condensed in bursts (i.e. can't cover everything in 3+ layers of mitigation), slap bleeds in there for good measure.

Simply put, more damage that can be reasonably reacted to, can't be covered by bloats of mitigation forever and can't be covered by tanks & Dps healing alone.