I already have a DK on my server and he's a Blood (tank) DK. I would love to have a Frost&Unholy one too because they are all amazing. Is it possible to get more than 1 Death Knight on a server? I don't remember. And if not, can you make a DK on another server w/o having another character on that server? I want the other 2 DK's on a PVP server also.

last i checked only one dk per server is allowed so you would need to make one on a new server or just fool around with your current one buy the duel talent spec thing

You cannot have more than one DK on a server.

However, you can make a DK on any server so long as you have a character of at least level 55+ on any server. You do not need a character on a server to make a DK on that server.