Prot warriors can do the same now, and they don't need to drink. I imagine Druids will be the best of all though since they can heal themselves, use rage instead of mana and can swipe unlimited targets.
While they can do it, Prot Paladins are better for a few reasons:
1: They can res you if you die (soul stoning yourself as a warlock can work, or self ankh as a shaman, but they have long cooldowns, and just 2 classes).
2: They still do more AOE Damage
3: They can bubble you
4: They can heal themselves and you if you are a class that can't self heal (say you are a mage, a warrior, rogue - and so on).
They also don't run out of mana either, as they get it back for blocking / dodging. This means that they rarely run out of mana, the paladin I had helping me only stopped a few times, and that was after masses of mobs at once in stratholme.
I am not saying warriors are terrible, and are a great choice (particularly if you are say a druid who can help heal him/her a little) but simply for your survival more than the warriors, I find paladins are better for boosting (I am not saying they are better end game, in DPS or tanking, as Blizzard are stating the class is even, I am talking about from a point of view who has been boosted by both).
In low level instances though (for example dead mines) it doesn't matter
