Also, I can't believe you used a scroll on your amulet of life saving XD
Aside from the obvious (those in the main chamber of the cathedral) you need to watch out for the smith. He is surprisingly formidable and what he lacks in equipment he'll make up in survivability. You could take him out first, then use the bottleneck of the cathedral to your advantage (don't take my word on this, I've never even gotten Elpuri's head back to Petrus, let alone kill him). You'll need some way to detect invisible units too.