I've been 2 boxing for a while now. My first 2 70s were a Prot Pally and a Priest. I had no problem while leveling, and in fact I would AoE grind quite a bit. Surge of Light and Holy Nova (Rank 1) work GREAT for AoE grinding - and the paladin's Judgement of Crusader on his target maximized the holy damage done, whereas sunders don't help at all. Right now I have a 64 priest and a 64 warrior that I am grinding up to 70, and it really seems about 10 times the work. Last night I was in Zangamarsh (which I am slightly overlevel for) and a "friendly" priest ran past me and AoE feared the naga my warrior was fighting - soon I had the entire camp on my head and there was nothing my warrior or my priest could really do. With a pally, I could simply run away, bubble when needed, and then come back to my group and res. With a warrior you have to make sure your priest (the clothie!) actually survives your battle. With a paladin as your tank you can have your priest healing with their last gasp ... and if the pally makes it, you're golden.