I liked the stage enough to do another run, this time without rainbow damage. The main difficulty was trying to get set up fast enough during the start of the fight.
Orb Conditions:
+1 when dealing elemental weakness dmg
+1 when dealing 9999 in a single brv hit
-2 on player turn
-2 on enemy turn
Without some off-turn attacker, you do not have any way to gain a net increase on the orb count unless you’re in BT or summon phase. This would mean you have to always be doing AoE Brv damage and to not let the bosses get too many turns.
At 79% and 49%, the bosses will counter heal and reduce brv dmg received even further. You’ll have to deal 9999 Brv dmg to cancel this.
The trick is to push the thresholds one by one. If one boss has the counter heal active, hitting 9999 on the OTHER boss will still count and cancel the healing. That way, you don't have to try and overpower the additional dmg reduction they have during the healing state. Obviously you won't have to worry about doing this if you bring someone that can do rainbow brv dmg.
I primarily brought brv dmg enhancing calls, including the classic Type 0 Jack call just like ye olden days. Everyone can reliably hit over 9999 so it was mainly a matter of trying to beat the bosses before BTs ran out.
—————————
Soundtracks used (I don’t own these songs):
-FFXIV Endwalker: “The Nautilus Knoweth”
-Octopath Traveler 2: “Fierce Confrontation”