Unable to complete Seat of Sacrifice (Extreme) with < 8 players (unrestricted party)

Date & Time: July 28, 2024 @ 8:42pm Pacific (but has been the case even since Endwalker came out)
Frequency: always
World name: Hyperion
Character name: Chai Latte
Retainer name: n/a
NPC name: n/a
Monster name: Warrior of Light
Class/Level: any level, but this instance we were all Lv100
Party or solo: Undersized party
In-game time: n/a
Area and coordinates: Seat of Sacrifice (Extreme)
Housing: n/a
Steps:
1. Load into Seat of Sacrifice (Extreme) with 7 or less people (no LB3 bar)
2. Fight Warrior of Light until the point where you would normally use LB3
3. Due to lack of LB3, you cannot survive, no matter the buffs you put on yourself or with echo, as the Ultimate Crossover damage is too much.

Old fights that required LB3 do not do this, such as Final Coil of Bahamut - Turn 4 & Alexander - The Soul of the Creator (Savage). They seem to use real numbers & take our levels/gear/Echo into account, so we don't just take "MAX_DAMAGE_LIMIT - shields/buffs" as dmg.

Example of damage log for SoS (Extreme):
https://i.imgur.com/uzm6C0S.png

Example of damage log for A12S:
https://i.imgur.com/thTrn9L.png

While I do not believe all old content needs to be solo-able, any content that a player can load in with "unrestricted party" should be clearable and not hard-blocked by lack of LB3 requirement.