Been using it through nightmare on act one, it's a little odd but it's working well for me.
I run in, get off the intel leach, spirit walk out, then alternate casting raining toads and dire bat. I use Zombie Wall if I have to to get out of sticky situations. I rarely run out of mana if I conserve it well.
Probably not the best build, but I LOVE hearing thunder and watching a torrent of toads rain from the sky and blow up on the ground. It's hilarious.
Anyway, tell me what you think. Would you give it a try?