Alternatives to the Role Actions System?

[Shurrikhan]

Just one thing, "Nothing better" does not equal mandatory.
Mandatory is something you NEED in order to complete the fight. Like, it is impossible (or it becomes extremely clunky and requires gimmick)
Provoke is mandatory because there are many fight where you need a tank swap and some fight put two tanks on different target making the swapping impossible without provoke.(Bismark for instance)

Shirk is not mandatory and not always interchangeable with provoke. There are many instance where 25% of your threat might not be enough for a tank swap (without provoke Ofc) and its long cd makes it an unreliable tool for frequent tank swap (shin claw for ex).
The long list contains no mandatory skill (spare interject for os3 add).

Can you name a single fight impossible to perfectly (no death) execute without reprisal, convalescence or rampart? By impossible I mean, the boss cannot realistically be done without seriously overgearing the said fight.
Same goes for healer. Although we say lucid dream is mandatory, it isn't. It is an extremely potent and convenient skill to have, but it is not mandatory. Without overheal and proper play, in my experience (up to os3) every fight is clearance without it (ultimate included, I've seen a video with a WHM pov. He didn't need it).

Esuna is, sometime, mandatory. And by that I mean you need it unless you consider rezzing people or letting their dps drop to nearly 0 for 1min part of the fight (see doom on OS4 or paralyse on shin for instance)

Dps have no mandatory skill, there is not a single skill that is needed to complete a fight. (again, useful doesn't mean mandatory, apocastase is useful, but there s no tank buster impossible to survive without it, for example)

I think this has turned into a question of semantics. Azure (as I feel most do) considered "mandatory" as skills without which you likely would or should be replaced from the group because they are just that much more important or powerful, not as skills without which you cannot complete the given content. The majority of even current content can technically be completed at minimum ilvl, undermanned, after all, but that doesn't mean that speed doesn't then remain an important metric.

Shirk, for instance, equates not only to increased safety (which generates slightly higher healer DPS, potentially, around the swaps), but to increased DPS in the vein of having an additional 2 Ninja's worth of Shadewalker and Smokescreen per tank carrying Shirk. To those who care about raid DPS, then, it ends up essentially mandatory.

I mean, if we want to go so far as technical mandate, even Provoke isn't actually mandatory outside of such early and instant swaps as T11, where critical strikes can do easily throw a natural swap into disarray. I managed to get through an Ultima Ex back in ARR where my Warrior off-tank didn't have Provoke. Luckily we already had the enmity meters by then, so we simply took hate from each other in a natural fashion, timed almost precisely to the 3rd or 4th stack as to time out our CDs ideally -- using Storm combos only as often as necessary to maintain Maim as OT, and using only Storm combos as MT once nearing the swap point. But there's no way anyone would accept that level of potency waste these days from having to use so many enmity combos... now that they're a significant DPS loss on all tanks.

The same goes for Lucid Dream; unless casting only Cure I, Physic, or Benefic, you cannot cast use every GCD without running out of mana, let alone continuously stick only to more potent heals and fill the larger number of downtime GCDs with damage skills. In casual content, it might not be necessary, especially if you already have access to Refresh and your casters take Diversion (far, far weaker over time), but it is disgustingly powerful and you likely should be replaced if you refuse to take it, as not taking it will cost you upwards of half of your throughput over the course of a 5-minute moderately intensive fight (much higher, still, for non-WHMs given their free oGCD throughput impact, Assize, and Thin Air).

I imagine that Neo ExDeath would very, very likely meet your criteria for a fight that will at some point actually require Reprisal, Convalescence (not for MT sustain, but for Deployment through Defiance Warrior, especially prior to the Shake it Off change), and Rampart.

The bigger issue to me, though, is why a fight would need be designed around or to include the benefits of some skill, tool, or system that isn't going to be interesting in itself. It's not as if the fight would need to remain tuned precisely where it was if those tools were buffed, nerfed, or removed. Nothing about any fight will ever obligate a design decision outside of it -- it simply scales its tuning with the tools available or expected to be taken. So even if a fight requires these tools, that's no defense of the tools themselves or the system holding them, should they reveal flaws or failings elsewhere.