There has been a talk surrounding the addition of the Death Knight class in World of Warcraft. This is quite intriguing especially since the new class' role in the Wrath of the Lich King expansion has just been recently clarified.

The hero class will not be a juggernaut capable of taking down bosses or entire Arena teams on their own. For all intents and purposes, the Death Knight is a normal character that starts on a higher level. It was made to give players a chance to experience the lands of Azeroth from a different perspective.

Blizzard Poster/ Community Manager Drysc gave a pretty good explanation on this in his post on the WoW Forums:

"Hero class" effectively means two things, and two things only. They are generally based, conceptually, on a more prominent character or class found in Warcraft lore.

They start at a higher level. That's it. Now we also want to do additional things, such as making them unique, making them interesting, and providing some very cool experiences tailored just for the new class.

These classes are based on some very prominent figures, and we want to make it fun experience. What "hero class" doesn't mean is that they're more powerful, they're going to be able to solo bosses, or that they're going to be anything but a new addition to your normal raid and dungeon groups.