We all know that you can swap souls to customize your character. But how good do you think a Rogue should be able to tank? Or how well should a Warrior be able to DPS? Or how well should a Mage be able to heal?
I personally think a fully geared Warrior spec'd pure DPS should do about 80% of the DPS of a fully geared and pure DPS spec'd Rogue.
I think a tank spec'd Rogue should be able to handle offtanking adds, or tanking in easier content when a Warrior is not available, but they should not be able to main tank hard encounters or raid content.
I would like to see the same type of ratio for Mage healing, Cleric DPSing, etc.