Huh, that means almost every dragon in the game is technically undead. I never thought if it like that.
Technically, only a few dragons in the game aren't undead when you look at that.
Alduin (He never died. Just was thrown into time).
Paarthurnax (No need to explain).
And there is a 3rd dragon you meet in Skyrim that shouldn't count as Undead... Can't remember his name but he is the very first dragon you kill at Whiterun. If you looked him up, he was never slain and kept hidden within Skyrim all these years. Only attacking a town now and then for food, and such. He became more active when Alduin returned, which caused him to get slain by us...
All others we meet were resurrected in some way or corrupted into that stage.
~Edit~
Miraak's shout is overpowered but would be nice to have to quickly dispatch dragons when you don't want them to attack cities and towns...