Well, if Wizards got healing spells, I think this would be more of an issue. But the spell Schools are really only relevant to Wizards and, personally--if it wasn't for the high degree of overlap between the traditional Arcane/Divine spell list--I wouldn't put 'Divine' spells in any school at all. Just use spheres, domains or paths, etc.
Personally, I don't have a problem with them being in Evocation, because this school is Evoking Arcane/Divine power in a dramatic way. I'm not a fan of Necromancy for healing, as Necromancy is more of death type of connotation rather than life and healing.