Okay, yeah, Lumine is impossible to beat now and may remain as such until the stats bug is fixed.
Started a new game in easy, rushed as much as possible to have an army ready to welcome her by week 40 (her second comming so that she wouldn't have many stats, I even went as far as only training attacks increase because of the bug), 2 unusuals with full stacks and 6 nyctos, also full stacks.
The nyctos manage to take down Paimon, then she goes into her second form and I'm doing around 10 damage with each unit while she recovers fully, then she uses her nuke and even if the unusuals block her escape, it doesn't matter because she cleared the map.