May have just worked out a safe location for Templar after the patch. At the base where you pick up the artifact, you can hide under the ledges. If your careful you can fire at the boss from this location without being shot back at. Due to everyone being close together its easy to cleanse. The harpies dont come down to you and you dont need to chase the oracles. If he moves to a location you cant see him, just carefully move out till you can see his arm while 2 members cover the ledges above you, as soon as the you need to cleanse, rush back to the safety of the ledge.