I love how Necromancers and Death Knights are too similar to each other, so Necromancers can't exist.
But Tinkers and Engineers are not similar to each other, so we NEED Tinkers.
Honestly, model the WoW Necromancer after Diablos Necromancers. Make a pet spec focusing on undead creatures, do a poison themed DPS spec (mixture of DoTs and DD), and, for some spice, do a tank spec. We haven't had a new cloth based class since Classic, and tanky cloth hasn't been done before, so it could be a fun. I see something like a drain tank, stealing defenses from their target to empower their own tanking abilities, a life steal concept to empower self healing, taking the forms of various undead to mimic their abilties, etc.
The idea has legs.