What you have picked is nice and all, but what I would have done would be:
Spitter - Skeleton (Due to ranged attack - possibly customize the spit model to be his arrow)
Smoker - Enderman (Due to height)
Boomer - Creeper (BOOM!)
Tank - Iron Golem (It wasn't available at the time but now it is, and its just perfect)
Hunter - Spider (The cawling would do good wit the spider low to the ground)
Jockey - Slime (Both the Slime's small size and jumping are better suited for the jockey)
Charger - ZPMan (For some reason...it works. I think its the sounds the charger makes)
Witch - ... (At the request of the description this is left blank)
Pros:
Cons:
Conclusion:
This review was posted before the latest release.