Encounter Design needs to be overhauled at a fundamental level

[Kalise]

however you have to realize that "base behaviour" of the boss is not "completely separate to the plethora of 'Don't stand in the bad' mechanics that define the actual difficulty of XIV's encounters." as you called it

Except, there's a little thing called how these mechanics interact. Especially in the scope of XIV.

In XIV, don't stand in the bad mechanics often result in death. Meaning healers use Swiftcast Raise. Irregardless of what the boss is doing (Otherwise, they often leave the person on the floor until Swiftcast is ready).

Otherwise, all Tanks and Healers are spamming DPS skills.

Adding more Tank and Healer duties to the base boss, doesn't change this. It still doesn't interact with the other mechanics, they're still going to insta-kill at the same rate.

The only difference is, instead of Tanks and Healers spamming only DPS skills, they're now also using Tank and Healing skills. The number of GCD's being used stays the same (Since, time between "Buster" skills and mechanics are not changing), the focus on pumping out maximal numbers of GCD's stays the same (Thus, positioning to account for the mechanics to run out of).

The only difference being, that there is now a minor level of thought going into "Do I press a damage button or a heal button" or "Do I press a damage button or a mitigation button" - With potential to create some overlap to allow for more dynamic gameplay at the higher levels (I.e. Stuff like a Tank going "Oh, some DPS need healing, I better pop a defensive CD so the healer has more time to heal them up before the next mechanic" or a healer going "Oh, the tank has popped a defensive CD, I'll use this time to pump out some extra damage while healing is less required")

Overall mechanics will continue being the same, irregardless and fight difficulty will still hinge upon those mechanics because at the core, the base mechanics of bosses will continue to be simple. Merely having healing GCD's be necessary instead of some damage GCD's won't notably increase difficulty. Especially when a LOT of the bad players already play "Pure Healer".

Can I be real? I don't like the idea of healers having to just sit back and heal.

Though, the general idea is for the balance of such a thing to be that healers don't simply heal 100% of the time. Hence why I suggested Tanks get more onus on mitigating their own incoming damage.

There can be a balance between damage and healing skills for healers, it doesn't have to be pure damage like current or a pure heal rotation.

It merely requires damage to be tuned appropriately, so heals are useful and needed to top off players throughout the fight, but without being so direly needed to take over the entire gametime of a healer.

Additionally, in such a scenario where more frequent healing is being used, there offers more space for gameplay designs such as the Lily system that can cause healing and damage to be intertwined.