Listen, wasting source points to give people a talent that generally sucks isn't worth it, especially since EVERY OTHER source skill has combat use. What good is turning your friends into zombies int he MIDDLE of combat? It's not.
Zombie should just be a talent, plain and simple. In part because much like Demon, it's not literal. It isn't actual undeath, it's just an elemental switcharoo.
Saying it shouldn't be selectable past level 1, or that you shouldn't be able to be it, or that it should be of all things given by an origin source skill are as ridiculous as saying the same things for Frost King and Demon.