I gotta say I love the Holy/Smite priest+Prot pally combo - that was my first Dual Box experience. If either person lives through the fight, you have a res - pally gets bubble and DI - so you almost never have to run back from the graveyard. On top of that, you get JoW on the mob and you can wand for mana, you get Seal of the Crusader which makes your priest actually get decent DPS, you get consecrate which means you can AoE mobs and simply have the priest heal through it.

Warrior + priest - your warrior will find it hard keeping things off his priest buddy. If your priest DOES die (which is often) the warrior can't do much about it.

Just my .02