Encounter Design needs to be overhauled at a fundamental level

[Kalise]

exactly because "only enough so they survive" is healer 101 it would mean you would have to top everyone off in the proposed scenario, you want to maximize the value of your global cooldowns

That depends entirely on your kit and what you have to spend to top someone off.

if someone is at 40% life

Why would someone be at 40% life? When random damage does 50% damage, avoidable damage does 100% damage and Raidbusters do (Currently) 90% damage. Or if you're referring to normal, then avoidable damage does 40% life and Raidbusters do 50% life.

When would someone be at 40% life?

You might have to heal someone for 41% life, if they got hit by a random attack and the next mechanic is a Raidbuster for 90% life.

Now, in the theoretical scenario where someone was at 40% life for whatever reason, maybe as a healer you might decide you can use an oGCD on them to heal them up while you're doing mechanics/using a GCD on the Tank/nuking the boss during a raid buff window.

With less potent oGCD's this might not fully heal the person, but they would still be above the 50% threshold that would let them die to this random 50% life attack.

Would you then have to heal them again before the next raidbuster? Maybe. It depends on how much life they have, how much self sustain they have, how many incidental AoE heals they have received, how much healing they'll get from the application of a Succor/Aspected Benefic shield (Which will be applied before the damage thereby also applying the heal before the damage is done)

Not to mention, how much damage raidbusters do with Tanks having more tools to mitigate them.

you wouldn't just "get them above 50%" because that would mean you would have to heal them a second time before the next group wide aoe or stack mechanic or whatever

That entirely depends on when the next mechanic is coming and what the mechanic is.

If another target is going to be getting hit by damage (Such as a Tank receiving a Tankbuster) you can simply heal both targets with an AoE heal.

If there's time before the next AoE, you can toss a HoT on them and so long as they're above 50% life, they're going to be safe from this random 50% life damage and if not, well they should be relatively healthy by the time the AoE occurs.

would mean i would have to use ogcds as panic buttons

Only if you don't bother casting a GCD heal and literally need to panic and push something to bring someone's life up.

in turn meaning i would again not have them ready where i want them (say a mechanic where randomly 2 people get targeted for attacks and need to be healed through them, or the next tankbuster, or as a general buffer for the tank/someone that messed up something else shortly before the next aoe.

Well... There's a reason why I mentioned shifting healing throughput to GCD's and not keeping everything on oGCD's. Since, Healers will now have to actually use GCD heals to heal things.

It's a shocking practice I know, but there's plenty of time to do so. Given that XIV literally cannot pump out damage rapidly because AoE's take time to travel.

Also, in even more general terms, the moment it can be screwed up even if this is do to complete failure on the players part it IS adding difficulty

It's the same as if in the current easy mode Normal raids, both healers decide to never cast a single heal, oGCD or otherwise, and focus entirely on nuking the boss.

Is this creating difficulty because people can be idiots and not be able to press a heal button and thus cause wipes?

Also what about mechanics that go wrong but do to sheer luck or whatever only 2 dps+1 heal die, now this other heal has to get up 1 heal+2 dps, this shouldn't happen, but it can and does happen.

If this is Savage/Ultimate, you've already wiped because you're not going to beat the enrage timer.

If this is normal, this is what Healer LB3 is saved for, to Raise and Fully Heal everyone and give full MP.

heck, all of this is even ignoring that even "random" can't be too random unless you want fights to vary between "easiest run ever" and "holy shit, how many more random bolts of death will he send?"

Not really. Even in my OP I mentioned having limitations to the frequency of random damage spikes.

Which can be easily sorted via cooldowns on the random damage after which point it CAN be cast, but doesn't necessarily have to be cast.

the scripted nature of the fights simply does not leave that much room to simply fill it with randomness, adding randomness means taking out scripted aspects

Not really.

There's plenty of time between "Buster" attacks where all that is happening is DPSing the boss and running out of crap on the floor.

That can be filled with "Random" damage because there isn't any other damage happening other than fluff damage from boss AA's vs the tank and potentially failed mechanics which in most difficulties result in insta-death anyway.

You don't have to take out scripted events either. Since again, there's plenty of room between currently prominent scripted unavoidable damage and again, in most difficulties, avoidable damage doesn't care if you're at 100% health or not it'll just one-shot you.