I agree the PZs will be available however you are then relying on getting a decent crow and you aren't creating more MZs, in regard to keeping the MZs near AoD just try to keep them in BtB with him and it really isn't that hard, basically surround AoD with a hoard and move as a solid block towards the enemy, that's how I would play it from what I can see..
Yep Seb's use is exactly that needing a 9 of anything, he is also no slouch in melee and can collect up corpse counters on the board to turn into body parts for Rafkin and himself. A Seb Rafkin tag team is a little scary. With 4+ PZs I'm not convinced a heavy hitter is necessary but if you did want one you could drop the original PZs and take a Rogue Necro.
btw has anyone else noticed AoDs lack interaction with corpse counters? What does placed mean in the context of restless dead? Say a dog or seb passes a corpse counter to AoD does it count as being placed within 6"? If so that's another use for Seb.