Why I feel the Priory wasn't handled well
SPOILERS INCOMING
I feel that the death of Zhaitan invalidated the Priory’s entire stance. They found no big helpful weakness. The biggest contribution the Priory made against Zhaitan was the Mega-laser which as far as I can tell was just a generally powerful weapon which had nothing whatsoever to do with the Priory’s findings. Zhaitan was defeated primarily through brute force and courage (Confirming the Vigil’s ideals) and uniting against the common foe (Strengthening the Whispers strategy). This leaves me feeling like the Vigil and Whispers were correct, while the Priory just screwed around and wasted time while people were dying. It also feels like a huge disconnect from the Personal Story for the Priory, where you find a dragon blood sword which could potentially BE that silver bullet, or at least something the Priory could refine into one. That sword is never seen or heard from again, and Zhaitan is defeated without it, making the entire expedition to find it feel pointless.
Now having the Priory find some magic macguffin which instantly kills Elder Dragons would be unfair to the other orders, but they should certainly have at least found SOMETHING helpful that ties into the final fight. A simple fix would have been to change the Mega-laser into some special anti-dragon weapon developed as the direct result of the events in your Personal Story, and actually mention it beforehand, instead of finding out halfway through the fight that “Oh, Zojja’s charging up a random huge laser that nobody mentioned before this.” The way things are now it feels like as a Priory character everything I did with my order was wasted time. Vigil and Whispers characters were bringing the humans and Charr together, while I was hunting down a sword which as of yet has no relevance whatsoever.