[Bruno]

There are specifically options for mystically empowered religious characters in Banestorm - it's not clear it's religiously empowered, or some sort of odd psychic effect, but it's there, and it's an option.

If you're not using that, you can definitely remove the two religious NPCs entirely without doing damage to the adventure. If you're using that, drop the cleric and either handwave the Holy Warrior as someone who is religiously empowered and Christian, or drop the Holy Warrior as well to keep things tidy.

There are orc shamen, but they're wizards.

The orcs don't have the orc racial template from Banestorm - it's up to you whether you want to run them as is, retune them to have the Banestorm template, or just shrug and say they've been mutated by exposure to the Mirror of the Fire Demon (dun dun duuuuuuuuun) and add that to the list of reasons to get rid of it.