As per OP's Question: The closest you can come is to have 1 of you be melee, while the other one is a ranged, there is no traditional tanking in TL2, and there is also no taunt ability or aggro tables. Mobs randomly aggroes in combat it seems, they will switch targets at random as well, and sometimes they will still to you like glue even if you are 2
Engineer has good team-utility abilities like Healing Bot and Forcefield, immobalizing copter is also quite good as a "team utility" due to debuffing mobs =)
tanking in elite is impossible
It's not impossible to "facetank" bosses in Elite difficulty, you just need to be geared, the best "tank" right now, is an Engineer with Residual Aftermath set which makes Aegis of Fate absorb go as high as 500k sometimes, but usually in the vicinity of 200k procs, Warlock and Berserker are quite the same, but a bit less tanky due to not having a 65k shield and Aegis of Fate procs, but Berserker very rarely dies and Warlock dies even less than a Berserker (All this assuming they all have their T1 gear min/maxed with special enchants and skulls ofc).
Having said that tho, the Paladin might be good enough to take the #1 spot of "facetanker" but i cant say since i have not yet tested paladin after hes rework so if anyone knows how viable Paladin is as a "facetanker" it would be nice if you could share your knowledge =)