The first black hole is the major wall right now. I hate to blame the healers since I know they have more things to deal with here, but they're the ones holding us back right now I think.
The healer with the stack marker will go to the center too soon and clip a DPS with their Fire III, or go in too late and they die with the marker, or sometimes we just all die to the marker because no one got healed after being hit with their Fire IIIs.
We've gotten past it sometimes but never without deaths yet.
The good news is that this is the 'right' spot to be struggling with the fight; if you were having issues elsewhere it'd be abnormal, but the first Black Hole is the think-on-your-feet part and where you should expect to spend the bulk of your prog.
Other people have already given good advice, but I'll tack on some more stuff:
- Not sure what your healer configuration is, but you can have a healer cast a shield to land right after Black hole cast finishes. You have a few seconds after the holes appear where they won't do anything, so the healer has time to finish the cast and then get to position. The shield will help absorb some of the Fire III damage. HoTs rolling helps a little too.
- As mentioned, Earthly Star/Assize/Indom are all really good for healing up for the stack. Star has pet delay on explosion, so landing the heal at the right time may take a few attempts, but it helps. Swift is great, and if you have an AST Lightspeed is A+ here. They should not be planning to hardcast anything before the stack resolves; it's possible to do but not necessary and by just planning instants the actual Black Hole spawn patterns should be irrelevant.
- Make sure non-healers aren't making it harder than it needs to be. As soon as DPS Fire 3 goes off, stack up tight. The less space DPS are taking up, the closer healers can be to the stack when they eat their Fire 3. I run on AST, so I plant a star mid and after DPS Fire hits, I run in and stand at the edge of the star. That way I can pop it when my Fire lands, everyone gets the heal, and we're close to the stack so running in is easy. If DPS stay loosely spread out, they can force healers to wait further out or do extra movement which makes stacking awkward.
- Utility skills are good here. Troubadour's Minuet will help reduce the damage everyone takes in that section and is literally free as the Bard should be in Minuet around there anyway. If you have a PLD, Divine Veil is an option. Mantra to boost the healing on the party at the start of Black Hole will mean slightly stronger shields, etc. These aren't mandatory or anything, but they can help.
- Everyone needs to make sure they have enough of a lead on their tether before they stack. The holes do not despawn until after Holy hits. If the tether is too short, the hole will continue to catch up and can clip somebody in the stack and one-shot them.
- Maybe take a couple of pulls solely to focus on positioning and ignore the healing part if you have to. Let the healers get a feel for timing, make sure nobody feels boxed in by the positioning, etc. don't even worry about surviving the stack, just make sure everyone gets there.
i dunno how western teams do it, but for some jp groups there are people that do the 2nd blackhole somewhere near the edge (i actually prefer this method) instead of the standard boss in the middle
when you do the 2nd black hole near the edge, whichever dps that gets flare will have much less down time compared to having the boss in the middle, because the edge of the arena is literally just 1-2 steps away
I think tank him dead center is slowly falling out of favor in the west, but unless/until updated guides with the better positioning PF will probably defer to dragging him to middle for everything even though it's harder than it needs to be.
But, yeah, edge or GTFO for the second set of holes.