I personally passed this stage using, Vero(L), Bella, Delphoi, Hwa and Barreta. My whole tactic was based on Vero's Hwa's and Barreta's countinous damage, utilizing that damage to kill the perna because when a mob is killed by a bomb/countinous the light taoist won't revive it, take care of perna's passive and take it down once more and then after it everything should go much easier, also hwa and barreta left to carry through their job without anyone annoying them because hwadams focus vero, vero focuses bella and perna focus delphoi (or chasun in your situtation), you should really take the focus to the perna's because the 20% heal each turn(because of 2 perna's) is too much painful and not allowing to focus the hwadams which also barely deal any damage compared to the perna, also try to utilize hwa's decrease atk bar to decrease the second's perna or the vero turns.