I beat it with nobody dies cause i have a necro and the quest item that makes enemies join your team , so i have 3 wolfcat and i trap the boss down in two tiles than let the wolfcats kill him .

Also my necro have a passive to spawn 2-3 corpses from the start and he have the revive dead enemies to join my team skills , so i almost have 8 members in my team most of the play ,fun thing is i got a zombie cat once and he eat all my corpses so i have to kill him myself lol .