I believe E-Heroes might be viable when we have access to Omni Heroes. Big and Little City variants are already too slow...Gemini Spark might make Little City viable if it's released, but that's all I can think of right now. Don't loose faith, we all know Konami has a thing for Dragons and Heroes.
Prisma would be interesting, but I see it being used mostly outside of E-Hero...the card pool we have at the moment is unimpressive. Neos variants would get a boost for Miracle Contact, but it's still pretty meh. PrismaGB would probably make a splash as well.