You should be able to do it, or have a great chance to. I would take Turtle Banners for the first few waves, then take Minor Mana and Mana, and maybe 20x Minor Healing.
Just make sure you TRY to kill the left or right boss first, so then you can still have Proteus working fine, so he stops the bosses.Be sure to stick proteus on the side of Kashhrek, maybe along with Sabina. So maybe:
Skittle / Sabina / Kashhrek / Proteus / 3*
I would usually put Sabina first but since there is nothing to dispel, it’s not needed. Or if you prefer, you could make sure your 3* and Proteus are protected by the extra healing from kashhrek, but honestly, it’d probably be a waste since they will die in 1 hit, so I’d focus more on keeping the other 4 alive… but that’s me.