In the original WoW beta, rogues were designed to be off tanks. Complete with a high dodge coefficient from agility and a buckler, rogues could survive quite a beating. Evasion was a tanking cooldown, and Vanish was a useful tank-swapping ability. Hunters worked similarly, also sporting bucklers and using Feign Death to lose aggro. Obviously, the developers scrapped both of these ideas before launch.
During The Burning Crusade, Gaeowyn broke the combat table by achieving unhittable status with 102.63% avoidance and using it to successfully slay Illidan. After that, the crew slew Gruul with just five people while it was still relevant content. In Wrath, Jider abused Shadowstep and our amazing damage output to solo several Naxxramas bosses. The upcoming Mists expansion looks to again revitalize rogue tanking, with the advent of the druid ability Symbiosis and our bonus ability, Growl.