I have been testing warrior and a paladin today and concluded that if you want to run high level dungeons to gear up your team a warrior is preferable because of superior mitigation, improved demo shout reduces mob damage by 30% and defensive stance by an additional 10%.

Paladins can block more attacks but against mobs that hit for 400 or more damage they risk dying if they pull too many mobs, and even though warriors take a lot longer to establish threat by spamming demo shout or cleaving/sundering your healer will use roughly the same amount of mana per fight because of 30% damage taken difference on hard hitting mobs.

So I agree with Apatheist, Paladins are superior in lower level dungeons, but at 55 plus dungeons warrior overtake them