Seeing as I haven't seen anyone do this yet, decided I'd try to do it myself. GElly makes autoing this a lot easier, but since I don't have her, I had to try and come up with a team. Apologies in advance for the terrible quality, I tried recording directly from my phone but it cut off the majority of the run, so I had to work around it. Anyway, as for how this team works & possible replacements:
Slot 1 - Xainfried (Lance Tank)
Lances here are great to have around, due to being mixed ranged so they have an easier time dodging Surtr's fire feet. The HP co-ability is also invaluable. I personally went with Xainfried due to him having the dragon time ability, his S2 giving extra dragon gauge, and having the highest base HP of all lances currently. You should be able to run other lances (I also did it initially with Fjorm, whose S2 sometimes times with a near lethal attack and does some nice damage), but success may decrease. Cibella is also notable for her shield, but has far less DPS than the others. Don't use Catherine, seeing as she has a high chance of imploding with her S2.
Slot 2 - S!Verica (Healer)
Basically the Grace of CoN at this point, her HP drain is what helps Xainfried recover after some of the near lethal attacks here. Run an off-element staff so she can focus on her healing. If you don't have Ramiel, don't use Bahamut instead, but instead use an 85% prep Alberius helper and run Shapeshift Prep over Crit Damage on Mascula (Verica has died on some of my runs, so it's safer to go with less DPS while retaining Verica's current kit). She's a little hard to replace due to her utility, but a 67MC Nurse Aeleen has the HP Buff, and Sandalphon comes with some nice healing too. I can't test either currently, though. Ricardt is also a consideration with his HP chain co-ability, though I can't test that either.
Slot 3 - Mascula (Dispel/DPS)
His strong standard attacks and semi-reliable dispel make him a solid choice here. He's also one of my favorite units to have around. If you want to replace him, depending on who your Axe is (I'll get to that in a second), either run another dispeller like Lapis or a frostbiter like Sharpshooter Sarisse (who also comes with a useful Str debuff). Summer Ieyasu has both dispel and frostbite, so if you got him while he was around, use him.
Slot 4 - Lazry (Axe)
The Axe co-ability is also important here, seeing as it greatly improves your survivability. Almost any axe can be run here, though preferred if they carry either frostbite or dispel. Pietro has neither, though he does come with a Dragon Haste chain co-ability and a shield, so you could try him out. Lazry is your best bet due to the frostbite & dispel at 67MC. Mine is actually only at 49MC, so my comp isn't perfect. In addition, the Poseidon on her is only 1UB, and you can run almost any other dragon.
The best skill share in my opinion is Cassandra, who brings damage and an HP Buff, followed by 67MC Nurse Aeleen, who has a heal and HP buff. From there, you have 4 options: Play with more fire by using Sinoa SS (extremely unreliable and a 70% chance to screw you over or 5% to give you a buff when CoN isn't up that still isn't great), run a dragon gauge SS (which I do here), run either Summer Ieyasu or Halloween Sylas SS, which pack both dispel & an affliction Surtr starts with 0 res to, or go with a Str down SS like Meene. It's honestly up to you & dependent on what you have. Also, Ramiel Helper for getting through phase 1 ASAP.
This took 14 recordings to do (plus a failed run I forgot to record, plus all the others before this which only has 2 other successful runs). Unlike the previous recordings I did, though, I got the Statue of Ilia to improve Verica's survivability & Lazry's DPS, as well as an extra node on Lazry. Both Impregnable Fortresses are also only 2UB, so survivability can be improved there. I feel like this can be a 60-80% consistent, or even more, but right now I don't have the Eldwater or Honey to figure that out.
- This run was both good and bad, as it has a break just as Blazing Resistance went up, but also dragoned for Crystal Firestorm, which is what kills most runs.
- In terms of bonuses, I'm almost maxed in facilities & less than half with weapons, just try to have that 7.8k HP on Xainfried and a good amount on Verica.
- For some reason, the AI will start exclusively force striking during some parts of the fight. No clue why this happens.
- If you have GElly, please just use her. It makes this fight infinitely easier to auto.
- Let me know if you find anything else out with this general comp on your own! I want to make this as good as possible.
Update: By the power of selling a spare MUB Shinobi from a billion pitybreaks by him, I got Lazry to 55MC. 5/9 runs, didn't witness first issue, second time was Xain unable to heal back enough, 3rd & 4th time Verica died. Times tend to range 5:30-6:30 now. In one of the runs Xain & Verica both died near the end but it still cleared (Verica got her HP drain up shortly before her death). Another had Xain die near the end, and still cleared fine. You can usually tell whether or not the run will succeed around the break, if everyone's alive then you should be fine.
Main things to improve consistency now is MUB the Impregnable Fortress prints, max Statue of Ilia, get Lazry & Verica to 70MC (extra standard attack damage is much appreciated), and to MUB Posideon on Lazry (or just use a different dragon entirely). Could also upgrade my altars to max, though water is 44/44 and shadow is 42/42 so it's not a huge difference at this point. Weapon bonuses also exist but are gonna be a bit of a pain to do. My math currently says I need 9k stamina to finish Agito alone, and there's still the matter of Rupies, Base/Void/Chimera, and High Dragon which I've only done 1 or 2 of.
Another minor note, my Water Dracolith is a little low on level, so I could probably speed up phase 1 more with that. I'll get that done with the upcoming double drops.