Enfys Nestm virtually invincible in the arena

My team: DV zeta g10 7* full mods, Palp g10 7* seta full mods, thrawn g10 zeta 7* full mods, tarkin g11 7* full mods
vs.
His team: Enfys g12 7* full mods.

the only way to keep him for destroying my toons: keep him for taking his turn.
outcome: even when enfys had 10+ debuffs and i used culling blade, still no damage...
this is ridiculous!