The Warrior its a DPS in fact but with a high capacity to absorb damage. The paladin is really tank oriented. While the drk its a dps but same as Warrior with a high capacity to take incoming dmg.

And to fit its lore the drk Always equipped heavy armors so the tank role For it, its good at least For me. Do not think that a tank its only defensive oriented. Its just the meat shield, or better the human target For mobs. But it dosent mean that it cannot do dps. Im healer and i honestly say that when i do dungeons with paladin it Goes slower than when i do it with warriors. That means that when u party with a Warrior in fact there r 3 dps and not 2. At least this is what i have seen during my adventures