Post-edit#4: 500 clears in a row after the initial set and 4x overnight x99 runs. Last 400 were full deathless by dropping the Crit print for HP70=Def+13%, to avoid the 1/100 revive change from the set shown in this video.
This fight is relatively easy to auto, but RNG deaths can still happen when you can’t target the Weak Point. This team setup avoids all of that and lets you survive the blast every time, giving a fully consistent AFK Auto. Required for 100%: High Chthonius, Vania, SVerica67, SPatia, most weapon bonuses on Lance/Axe (Wand/Staff can easily use more def prints). SVerica’s Lv4 S1 will preemptive heal keeping you fully safe against the blast and also gives a HP shield, but Lv3 doesn’t do either of these. Trying this without SVerica at MC67 requires a lot of adjustment for lower success rates (more defensive prints, Cibella SS to increase DPS uptime).
Recommended (lower success rates without these): Lathna, FNoelle/HMelsa SS. Poison Res down speeds things up but isn’t needed, but you’ll need SPatia for sure without this.