Once upon a time there was a concept developer who came up with the idea that the warrior class should have a bit of a berserker in them. A warrior should become enraged if he/she was being hurt.
Even though it sounded like a great concept, eventually warrior tanks ran into problems. They were being starved for rage, and so they had to remove some of the mighty armour that protected them in order to become properly enraged and inflict damage.
That was, in general, considered as a bad thing.
Having seen problems like these evolve over time, the very same developer visited someone higher in the hierarchy of those who had, among other things, created the warriors.
"What do you want?" asked the boss.
The developer rolled his head slowly, a string of spittle stretching from his half open mouth towards the floor.
"Ah, I see you have come up with a new and daring concept." said the boss.
The developer nodded, eyes glimmering with a frightening absence of coherent thought.
"It must be a grand idea indeed." exclaimed the boss. "Implement it! It is my wish."
And thus was it decided that all tanks, not only the warrior variant, begat something berserkerish about them. Whenever a tank is hurt a desperate need for revenge grows, and the tank hits back harder.
Astonishingly enough this resulted in a pecualiar problem. As time passed, all tanks noticed that they were becoming less and less vengeful, and that as a result they didn't hit things as hard as they had used to.
Three out of four tanks knew that some tanks had whispered dark words about a very similar problem, and so those three fourths turned to their warrior colleagues. And lo and behold, the warriors knew the answer.
"Remove the mighty armour that protects you, and you shall become properly vengeful again." they said. And all tanks concurred.
And the healers groaned in dismay, but as healers are prone to groaning noone took much notice.
This, my dear reader, is the reason I'm carrying four sets of gear in my bags, two more than I should decently have. One for quests and tier 1 Cata heroics. One for BH, tier 1 raids and the troll heroics. One for PvP, and one for raiding. Because, you see, my raiding set, the very best gear I have, isn't good enough for tanking content I should be bulldoozing through.
And this, my dear reader, is why one shouldn't have drooling retards as concept developers in a computer games studio, and expecially not a management who would agree to their idiocies.