[Messianic]

For group encounters, it really depends on which encounter you're facing. Sometimes a paladin or SK tank really is a better option. Sometimes you've got such a good group composition (i.e. Chanter, Cleric, Warrior, shaman, + two hardcore dps, etc - or one of the other great composition combos) that it really won't make a difference and having as beefy a tank as possible (i.e. a well-equipped, dual proc-wielding warrior) is better.

And if you've got a paladin or SK who knows how to use his periphery skills, or a warrior who's so fast on the taunt button or so quick at peeling from healers/etc, that player's skill (defined as attentiveness, knowledge of class skills and other class' skills and how to react to the situation at hand) will override the advantage of having the more "ideal" tank class for the encounter.

Just play whichever tank class you think will be most enjoyable to you in the long run.