Tanks should be interchangeable with the only differences being abilities and playstyle - but one should absolutely never be better than another at single target versus multiple target tanking. I don't see how they would even make that possible, since the tank that is good at multiple target threat won't be any worse at single target threat... but the single target tank will have a LOT of trouble when leveling, gearing, etc. when they are the only tank in the party.
People who play tanks should learn to play them well and with skill, but SE could facilitate the process a little better by making both tank classes a little more equal. It *does* seem like warriors have a much easier time of it than paladins with multiple targets.
