I personally played with different iterations of this deck concept, and I can assure you that both Soulcial Studies and Demonizer (but especially the former) are way better than expected, even in a class with Dark Arts.

While you shuffle Soul Fragments into your deck, you fight against aggro thanks to the Imps you summon and, in you're lucky, a bunch of discounted Demons from Demonizer.

Passive Treasures suggestions - go for All Together Now (get your Demons out of hand faster), Recycling (nice recovery tool for an archetype that summons lots of token from multiple effects), Battle Totem (look at the value) and Emerald Goggles (see All Together Now).