I need a break here and there to get more demon crystals and platinum armours and gold armours and such. But as far as completing the second to last map goes: I don't have a ninja either, but I 3 starred it both attempts by using Rowanna (she has a self-heal, and when she gets damaged enough she just tears things apart). I got two heals off on her, then retired her and let the rest of my crew finish it off from there after she had taken out all the hard stuff.