If your Gala Elly isn't fully spiralled and/or your facilities and weapon bonuses aren't fully maxed, you can replace the bufftime print for +10% flame resistance and the crit rate print for defense/HP if survivability becomes an issue.
I'm still doing some tests, using Summer Marishiten instead of Gala Poseidon for GElly since there's still a lot of room for improvement, and the runs are definitely faster with her thanks to the strength amps. But any of the two works.
As for the rest, I'm using GnC on SIeyasu (since he needs to dispel Surtr's regen ASAP, and having faster frostbites help remove his shield stacks faster) and Tiki with whatever is your next best dragon, 5UB Leviathan is really good for this if you don't have a MUB SMari/GPos for her. SVerica can use either Bahamut or Ramiel for the dprep.
As for the shared skills, I'm using Mym + either GLuca or HMerc (since SMari doesn't benefit as much from GLuca's SS guaranteed critical hit as Poseidon does).
It has been 100% consistent to me, although results may vary depending on your facilities, weapon bonuses, encyclopedia, etc. Nothing short of an oneshot can kill you thanks to SVerica's healing + lifesteal, and the strongest Surtr attack will at maximum drop your GElly's health to like 1k health, but will never kill you and you will regen back to full instantly. Also, the run is so fast that there's little room for variance so it's been extremely consistent.
Very rarely the run will take 30 seconds longer if Tiki gets out of shapeshift right as he summons his shield since then they take forever to break it, but besides that, the average run takes between 2:00 and 2:20 minutes at 2x speed.
I'm at 500 prisms already just from doing all sorts of test runs, and I've yet to see that comp fail once, because like I said, there's simply not enough damage to kill GElly if she's decently build and with Impregnable Fortress, since she goes back to full instantly thanks to SVerica's regen + lifesteal.