Does tanking carry more responsibility than most?

[JonBigwood]

My opinion is that it's the easiest job around, ONLY AFTER you learn the fight and the team is entirely comfortable with your positioning and skill rotation.

Therefore, the first times you do a dungeon it is not that easy job.
Easy dungeons may be easy from the first try for many classes (unlike for the noob tank, a tank that is level 50 other class has a lot of the way done), hard ones have difficulties for all, but tanks good or bad work makes a lot of difference.