I think at least artificer should be in the game. Most of act 3 is basically about artificer. The Iron Hand, the Gondians and Gortash are all artificers, yet that class is nowhere to be seen. It doesn't make sense.
Well, I guess we now know it won't happen. Patch 8 is the last patch. It's a shame, since Artificer has so much multiclassing potential with a Wizard. I'm thinking Alchemist/Transmutation school, Armorer/Abjuration school, Artillerist/Evocation school, Battlesmith/Necromancy school.