With so much necromancy in one place, it's only a matter of time before a league of Paladins storms this thread to cleanse it permanently. So, we'd better be quick.
Create Undead is pretty much useless as written, for reasons already discussed. My fix is pretty simple: Create Undead can create any undead creature up to 12 HD, making it the undead equivalent of planar binding. Greater Create Undead raises the max to 18 HD, while a Lesser Create Undead variant can be added with a 6 HD cap.
Problem solved: flavorful intelligent undead-creation for your BBEG Necromancer that actually works.