My setup is as follows:
Mystic Code: Chaldea Combat Uniform
Cu Alter (lvl 100, NP 2) - LB Shana
Hans ( lvl 65) - LB Carp
SUPPORT: Waver (lvl 90, 10/10/10 lucky me) - Carp
Fill:
Irisviel (lvl 73) - Carp
Mash (lvl 60) - Carp
SN Cu lancer (lvl 70) - Carp
Basically, I farmed 2bp until I could one shot her at first turn. I then went to 3bp and my strategy is as follows:
First mob: build up as much NP as possible without using any skills, they don't hurt and it doesn't affect your turns with Oni. When I enter battle with Oni, I usually have my first 3 servants all with NP (after using Waver skills) and do as much damage as possible to Oni (now Cu Alter 300% NP does about 1.5 mil with my setup on first). I take down the hands unless I get a Cu Alter brave chain and I use that on her. I make sure hands/Oni have 1 charge before using my NP chain so Waver takes away a charge.
Once hands are gone I blow up Oni. I use every NP as soon as I get it I don't wait to stack. When she has 4 charges I use Gandr (Stun) so essentially I get 5 charges before she uses her NP. When stun wears off I swap either Hans or Waver (whoever has more HP) for Mash, use her Invincible on herself and taunt. She lives and I keep at Oni.
For her 2nd NP its kind of Russian Roulette. I basically use my best judgement as far as holding my Evasions (Cu alter, Cu Lancer) since they negate her NP and use Irisviel Invincible if she is up, essentially giving me a 2/3 chance no one gets killed (Unless all 3 are up, then no one gets killed). Best I've done with this setup is kill all 6 million HP with only Hans and Waver dying.
Hope this helps.
