With the coming of Wrath of the Lich King, many are afraid about how class synergy will work. In this case, the question all boils down to death knights and how they will assert themselves in a group. Will death knights be able to coexist with the other heavy-armored tanking and dps classes, especially the warriors, who look to be the most affected by the advent of the death knight class?

While we can't offer any answers to the question as yet, we can give you some talking points with which to ponder on. According to a recent post on the forums, it seems as if the community managers are expecting Blizzard to turn the new class into something that stands on equal footing with warriors and paladins, rather than someone who overshadows the other classes. Here's what CM Bornakk had to say about the issue:

Right now we have several options for classes that can heal, dps, or tank and all of them are playing alongside one another very well so I believe Death Knights and Warriors will "coexist" just fine. I can't see having both of them in a group and just constantly dueling because they refuse to do so.

By adding another dps/tanking class, the Death Knight will give players and groups more options for what they need to complete their objective(s).