Ultima HM is really frustrating

[Low_Kick]

Although the bits do not fire their lazers at the same time, after the LAST bit has fired it's lazer, there will be about a 3-4 second window that you can cast your heals, that timing is what you should strive for.
The following strat is one that I came up with and it works extremely well for me whenever I run this. If you aren't in a static, you need to let your party know a few things.

1. If you are with another whm, figure out who is healing the main tank, and who is healing the rest of the party during the bomb and lazer phases. I personally ask the other healer to heal the tank while I heal the party since I am comfortable with the strategy I have. If you are with a sch, definately make the sch heal the MT, while you as whm heal the party during those phases.
2. Mark yourself with a sign. Tell the party to follow you during the bomb phases, and tell everyone to align themselves so that when Ultima uses aetherial boom, they get pushed to the south. Also tell them to activate the bomb you are close to when they see you start casting cure III, that way cure III will hit the party immediately after the bomb bursts. One cure III will heal the group to full hp. Detonate the North-South bombs first, then the East-West ones after. Let the off tank know either to go with the group, or stay away from the explosions, the OT doesn't need to explode one by themself.
3. As whm, cast protect on anyone that is raised, as we have shell with it aswell. If the other healer is a sch, let them know to cover the tank so that you have time to cast protect during battle.
4. Make sure to use focus target on Ultima so you can see when it does aetherial boom to position yourself to get knocked back to the south end, aswell as tank purge so you can precast your med/med II.

The reason I mentioned the above strategy, is that it makes the fight easier, aswell as the transition to the 2nd lazer phase easier. Since you are topping everyone up with cure III during bomb phase, there's no chance of someone solo'ing a bomb and dying, also saves someone from dying afterwards from either the green balls/ green line lazer, or tank purge right before the 2nd lazer phase.

After the bombs and green balls, Ultima will tank purge and it goes to lazer phase, make sure to precast medica II, and throw in a medica right after. If everyone is able to avoid the lazers, they should be full or near full health for the arms that come down on the sides. If someone does get hit, you can cast a cure on them in the window I mentioned in my first sentence, and you can also regen while running. For when the arms come down on the sides, you can do either a medica II at that moment, or if everyone is bunched up on top of you in the middle, you can cast a cure III, you will have to precast this aoe though. After that, it's more dodging lazers while getting in cures and regens when needed until the dps kill all of the bits. Once you get the timing down on this phase, the rest is cake.

If you are dealing with a sub-par co-heal or a sub-par tank, there are a few things you can do during this phase to help. You can divine seal+regen on the main tank, use eye for an eye, and virus if needed. You can throw in some cures if really needed as the rest of the group should have medica II still active, but make sure the dps's hp are near topped up for when the arms come down. Save your benediction for this part just in case too and use it if tank gets 1k hp or less. I tend to save presence of mind for in case Ultima goes on countdown to enrage, I spam stone II with it. If you are designated on party healing, and you are weaving in and out of lazers while casting heals, and the tank still dies, then there is a problem with either the tank or the other healer. Make sure the tank saves cool downs for this phase since both healers need to be moving around alot, have them save hallowed ground for this specific phase. Make sure the other healer is aware there is a window between lazers shooting that they can get healing in, and if needed they can eat a lazer or more, depending on their hp. Make sure they are also saving their cooldowns for this phase, as it is the hardest phase to cure in since you are constantly running around.

[synesthetic]

For bits, I usually have no choice but to use only Medicas, standing roughly in the center while hopefully still close enough for Med to hit the MT. Your DPS is hopefully rational enough to focus down bits one or two at a time so that there's less to dodge as soon as possible. If I'm in midcast and just one laser beam ends up falling on me, then I stand still and let my spell finish because each bit doesn't hit that hard.

Priority is still always on the MT though. Cure2 as needed. If you see green lasers, then top off the MT and be ready to Stoneskin after the third laser since Diffractive usually comes a few seconds after.
On that note, I never spend Swiftcast on Med. I save it for raises since most tanks I've seen are death-prone to Diffractive, often not knowing when to pop cooldowns for it, or getting brought down to double-digits even if they did. And then there's the occasional player who's lagging and gets hit by Ifrit's charge or something.

[erasure25]

Try moving a tiny bit out of the laser's path and be trigger happy on the cure. You should be able to cast before the next laser hits you. Doesn't always work, but if you just move a little bit and then cast immediately you should be able to get a cure off most of the time. Also, you can move before the cast animation completes if you move right when the cast bar gets close to zero.

[Kyomih]

Due to how the server handles checks you can actually cast and move before the cast ends. It will still go off
It takes a bit of practice but once you get the hang of it it's easy to get a cast of while dodging lasers. Even a cure II.

During the first set of lasers you want to be all the way out to the side but close to the tanks so you can dance but still reach the MT easily.

Also, make sure your tanks know how to dodge..lazy tanks on this fight can make it hell for a healer.
Again, assigning one healer to do MT healing and the other focus on the group while both help out if one gets into trouble works really well.

However, this is really a teamwork check and if your dps get hit by things they can avoid all the time it's not really your fault

[aivedoir]

The 2nd laser phase is easy - as a Scholar I focus heal on tank while the whm raid heals. When the 4 airships drop and people run to center, I throw Sacred Soil there and keep spam healing tank while whm Cure III everyone. Spread out to avoid lasers as soon as those airships hit the ground.

In my experience, groups wipe there when the healers don't communicate and overlap heals too much on either the tank or raid.

[Nukocafe]

I'm amazed you have a problem with yourself - for me it's always some tank who doesn't understand how to use cooldowns or has terrible gear and ends up dying and then therefore wiping the party. I'm a scholar though and the best advice I have is "stay out of the fire" and during the laser bits run somewhere where you are in the range of being able to heal the tanks.

With the middle lasers portion - run into the middle where there's no lasers and continue to pay attention to where you should be standing until the ships drop.
Soon as you can't see the lasers and ship drop animation happens you should be RUNNING AWAY.
You do not need to "stand in the middle" until the airship animation finishes and by doing so you're leaving yourself susceptible to a laser.

Essentially it's "ultima's ballad" and well you'll be finding yourself "dancing around the room" most of the run

[PetiteMalFleur]

I main WHM for this fight and this is the most difficult it part of the fight to heal through. Your PLD tank needs to save hallowed ground for when the second airships come down. (Holmgang for WAR?) If I am pugging a group I will ask the MT to save their biggest cooldowns for this phase.

For my own strat I will Divine Seal > swiftcast cure 2 as the bits spawn. I then place a buffed regen on the MT, E4E and virus Ultima. With all the debuffs up cure 1 is enough to keep the MT up while throwing out an occasional heal to dps who get hit by bits. If things get scary I pop PoM and start spamming cures. After airships I will aoe heal the raid again and help top off the tank.

[ZoroRoro]

I main WHM for this fight and this is the most difficult it part of the fight to heal through. Your PLD tank needs to save hallowed ground for when the second airships come down. (Holmgang for WAR?) If I am pugging a group I will ask the MT to save their biggest cooldowns for this phase.....

I do this fight as WAR and SCH (MNK less so), and from both perspectives (and perhaps because I'm no pro at either), it is definitely startling how quickly a tanks health may drop after a vent-diffractive laser sequence; one of these always seems to occurs just when you breath a sigh of relief having dealt with that crash and tank purge. Tanks definitely need to help out the healer here with their good CD usage.

Perhaps more appropriate for the tank forum, but from a WAR perspective its probably more situational what CD you use and may depend on gear. In addition keeping SP up, definitely want to IB before the crash and then use another CD. I've found can get away with just doing Thrill of Battle+Convalescence as well if you're close to being topped off and you're in a good position. If my health is closer to 2/3 with ToB up (so ~6667/10000 ish for me) I toss in vengeance if I have it, or (bleh) foresight. Otherwise better to stagger these CD though if you are in a good position in terms of HP.

I only consider using Holmgang up front if I don't think I'll survive the crash. Holmgang carries alot of disadvantages, the shorter duration, the root, and the fact that your health may be at '1,' (I've seen alot of healers unfamiliar with this ability just give up thinking that I died... good reason for a sound effect macro I guess). The 1st few times I tried it out, I either did it too soon or I rooted myself with about 6 or so lasers pointed at me and I'm still locked even though the invulnerabilty is over. I now like to save Holmgang in case I hover at 1/3 health after the crash for extended periods of time - its tough to stay this low and stay alive with the various attacks and diffractive laser coming up.

[Hekmatyar-Koko]

I find the lasers to be rather easy - even if I have them all on me, I can always stop and get of a heal. ALL the lasers fire on an easy to grasp rhythm, and your heals can fit in nicely. As stated above, you simply need the cast bar to hit about 8/10 complete and it will still go off, practice outside of combat if need be (or just try it when everyone is prepping as I think the latency in Ultima is improved vs in zones). Simply need to remember - any 'latency' that you blame on enemy AoEs hitting you, also works the exact same in your favour.

Lasers appear > move slightly > cast to 8/10 > lasers appear > move slightly > cast again > repeat. If need be, take one laser hit - one won't kill you. If you cannot get a heal off, use Regen at least whilst moving. If you have all the lasers then the other healer should be having a much easier time.

I've also never had an issue with a tank getting too damaged by the airship, if they move to the midpoint of the landing zones on the outside, they won't take too much damage. By then enough lasers should be down you can precast a heal on the tank anyway.

Also, when the green lasers start appearing, simply run behind Ultima (or to the side) as it only cast them in 45°, 90° and 135° from where it is facing. Even standing slightly in front and slightly to the side is easy enough to dodge.

[Raestloz]

I usually encounter another WHM for Ultima so I don't know if it is more because there are 2 WHMs or not, but I usually can still cast something amidst bits, there is always that tiny piece of land between the lasers. I know that I can move half a second before the cast actually finishing (probably due to lag) so I do it. In the event I can't move, 3 bits won't kill me, each is just about 400 or something, no biggie.

I have more problem with tanks dying after Aetheric Boom.