When he's not taking the piss out of diehard Diablo II fans, Diablo III lead designer Jay Wilson is all about classes (and probably other topics, but classes for now). In a chat with MTV Multiplayer, Wilson explains the exclusion of the Necromancer from D3's lineup, and the possibility of its return in the future:
"There's a lot of people on our team who aren't happy with our class choices", he admitted. "But after we've established 'Diablo III' as its own game with its own type of gameplay and experiences, I wouldn't be opposed to looking at old classes. We are trying to design [the Witch Doctor]class so that if we did bring back the Necromancer, there's room for him. We're looking out ahead of time at what our expansions are going to be, so we've got to keep room open for some of those other classes down the road".
Wilson also mentions that the team wanted to avoid having an excessive number of classes, and that main reason the Barbarian made a return was because it felt they could bring something new to the character.
I can understand not wanting to cover the same ground twice, I just hope the push to come up with completely new classes and mechanics doesn't result in an overly convoluted design.
'Diablo III' Designer Explains Why Necromancer Was Cut, Hints At Return [MTV Multiplayer]