I'm a level 50 juggernaut, I went from 10-43 as immortal, then I went rage to finish up 44-50 now I sit at 50 still rage spec'd, I deal an insane amount of damage due to how centralized my stats are (Very high power / surge = giant force smash crits)
As for juggernaut tanking, I've noticed they have the least amount of perks towards actual tanking when specced fully into immortal and actually hinder their ability to hold aggro due to low damage!