Ultima HM is really frustrating

[Nekodar]

Other than that, it's important for DPS to stay alive the whole match. If any DPS is down for an extended period you aren't going complete before he casts Ultima. An over-geared group can compensate for that, but for the most part any DPS going down is gonna ruin the fight.

Not sure what happened during my runs at Ultima HM, but I didn't actually see "it" start casting Ultima even once...
That's after the last set of bombs with tank using LB, and I switch over to cleric's stance and start tossing stone 2 at "it".
Got my healers ring after second win :3

[PenutButter]

This fight is definitely one of the most challenging for healers, especially if you're other healer blows. Fortunately, the fight itself is not that hard. Trying to heal the tank while dodging things like Ifrit can be stressful, which can be alleviated by good tanks. SCH has much easier time with this than WHM due to Lustrate and, to a lesser extent, the pet.

[whiskeybravo]

Not sure what happened during my runs at Ultima HM, but I didn't actually see "it" start casting Ultima even once...
That's after the last set of bombs with tank using LB, and I switch over to cleric's stance and start tossing stone 2 at "it".
Got my healers ring after second win :3

Ultima is cast after 10 mins.. Like a enrage timer. Good dps and you'll never see it.

[kukurumei]

This fight is definitely one of the most challenging for healers, especially if you're other healer blows. Fortunately, the fight itself is not that hard. Trying to heal the tank while dodging things like Ifrit can be stressful, which can be alleviated by good tanks. SCH has much easier time with this than WHM due to Lustrate and, to a lesser extent, the pet.

Sch can do fancy worth with lustre, but succor is even better in ultima.

There is a good amount of RNG even with i90 people, but it's mitigated by good teamwork. There are only really 2 times a tank can die. Outer bits(lasers) and Bombs 2 (from unlucky tank purge)

Healers don't have to be good so much as the rest of the pt needs to be good. Ifrit need to be dodged if it's coming from behind the tank. Bits (especially outer) need to be downed fast.

Pld's stoneskinning each other usually helps a lot in certain phases. As with dps that can focus and kill bits quickly, as with Melees that don't get floating bombs hit.

Healing is actually quite lax, if you simply save your big stuff for the trouble spots, but nothing will work if the other members are derping.

Ifrit dash
erruption
lasers
bombs

Those are the normal hurdles. and most of them can be mitigated by good teamwork.