It was tough doing a team of death knights when I was trying them out. Its the 1 DK per server limitation. I had to go delete all my DKs on the server to create my new team.

But then again rumor has it you can have as many Death Knights on a server as you want, you just have to create them on other servers and transfer them for an extra $25 each.
http://us.battle.net/wow/en/forum/topic/7415646336