personally, I find that they're almost impossible to kill because of their annoying habit of flying away when you try to hit them. that it until I discovered a handy trick: after completing the theives guild questline, get the shadow cloak of Nocturnal. After that, reach level thirty and complete the deadric quest for Boethiah. once you have the Ebony Mail, equip it and get to where the Dragon priest is. once there, activate the shadowcloak and enter sneak mode. once invisible, get close and try to bump into it. It'll look like it knows where you are, but the idiot will just stand there and slowly die from the power of the ebony mail after attacking you only once. and that's how to beat them. However, it would be best to bring along a few potions that will weaken the power of their cloak spell. I hope some one thought that this was helpful
In theory only Zahkriisos could be disarmed using the shout until a certain point (level 30), as he is the only Priest that levels between 25-60. But there's nothing to disarm, because he doesn't use a staff.
The Disarm shout indeed wouldn't work on the others, unless there's a mod I'm not aware of (only played on 360).
The Disarm shout would work if you have Thunderchild installed. It's a mod that allows the increase of damage done by shouts. Up to 200% more power for each shout. When I was using that mod, I was able to disarm even Draugr Death Overlords with 3 words of power, and they're roughly the same level as Dragon priests I think.
I wonder if, with that mod installed, Unrelenting Force is considered the MOST devastating shout, with Force w/o effort AND Dragonborn Force imbued together. I know Storm Call has the highest damage, with that said.