On par power mei mabui tenten gnw azure fang let you easily beat it if you own initiative. You use tenten gnw after the last standard attack of round1 and you use mabui mystery on the weakest healer in round2 as soon as the round start. It's almost guaranteed that the ninja is dead or close to be. If is not you add also mei so that the enemy is compelled in using both the healing mysteries. This let you redo the same move in round 4 with a guaranteed success this time since mei mystery can't be countered this time. With two healers left you very likely reach round 10 with higher hp than them since you heal quite a lot too or you are able to nuke one of the other two healers, usually azure fang, in round 6 or 8.