Why are so many people whining about the soak order? His is as easy as it gets. Who gives a shit about Cauteize, or Demo Locks or Divine Protection, there's a Rogue, Hunter and Spriest in there so its already a joke. All he's doing is alternating the Mage/Pally immunities on the 3rd and 6th to avoid having to top them off.
The only thing I might change OP is a Disc Priest instead of Shaman if you're lacking on DPS still, that depends on what pugs you can reliably get. If you get a pro Pally you can even solo heal it for more ease of DPSing. Oh and also spec switches that up DPS such as Arms War instead of Fury etc., but remember not to stick too tightly to that. So long as you have an easy soaking order and good players you're fine, don't turn down am experienced player just because they might play the wrong class.