Dark Worlds won't work if it's for a cost, like with Snipe Hunter or Lightning Vortex. However, they work really well with cards like Trance Archfiend and Fabled Raven, as they discard as an effect instead of a cost.
I've tried chaos hunter which clearly doesn't work. Would no.10 Illumiknight work? Its UR so I'm bit reluctant to use my ticket.