The vampire bothered because Durkon* wanted an ironic place to kill Roy inside of (plus more vampires) and probably wanted to kill him in person. The Order went to the temple because it was their only way into the city. They attacked Durkon* rather than go to the council chamber because they didn't know he had sent vampires ahead and they didn't want to give him a chance to kill more people (I think).
You know, I just realize that it makes a whole lot of sense for Firmament (meaning sky) to be the highest city of the Dwarven Lands and the seat of the Priest of Thor: Thor is a sky god.
Dwarves live monger, that means they have more practice at being old.
Yes, probably. Two of the Creeders prepared the ambush and it's later confirmed that it meant accelarating vampires. One of these two is with the Ex-Exarch and it seems reasonable that he preapared the spell as well. Dominating these guartds insteas of vamping them was probably to avoid giving it away to the Elders.
That's the point don't you think?