There used to be a saying amongst healers: "It costs less mana to rez a rogue than to heal one." Rogues were the only non-plate melee class (shaman and druids were healers), and our leather armor didn't absorb heavy blows. I remember gearing my first rogue specifically for stamina and fire resistance. I wouldn't be invited to the raid unless I could meet the 4,000 HP minimum health requirement. If I accidentally stole aggro, I would be squashed like a grape.
Times have changed. Rogues are now the most durable melee class, and it's not even close. Enhancement shamans and fury warriors can't toss on a shield without severing all hope of dealing competitive DPS. Rogues are capable of dealing nearly their maximum damage while taking less damage than any other class in the raid.