In the latest episode of Blizzard's Blizzcast, World of Warcraft lead game designer, Jeffrey Kaplan reveals that the Death Knight was one of three out of twenty-nine hero classes considered for the recent expansion.
The Wrath of the Lich King expansion pack flooded the World of Warcraft serves with Death Knights, but it might not have wound up that way had one of the other two hero classes that made the final cut had been chosen.
"We were talking for a while about a Necromancer. He would kind of be a range caster, do a lot of corpse explode, that sort of thing. Things we ended up incorporating into the Death Knight.
"We also had a cool idea for a Rune Master. That was going to be more of a melee type - think rogue or monk type character. But Death Knight ultimately fit."
While I would have personally killed someone with my bare hands for a monk class in World of Warcraft, I think they ultimately made a wise choice, even if no one knows how to play a Death Knight yet.