Mono-Black Midrange has no red spells for Blue Elemental Blast or Hydroblast to hit, but Pyroclasm still cleanly kills Withered Wretch, Hypnotic Specter, and Ravenous Rats, and catches a Nantuko Shade that isn't pumped in response. Mana Leak and a Daze are weak answers to a deck full of cheap disruption like Duress and Cabal Therapy that can strip countermagic from your hand before you get to use it, so they come out for the sweepers. Keeping the remaining Daze in can still trade a card for a card against their creature-based plan. Prioritize Survival of the Fittest to find Gilded Drake as a clean answer to Nantuko Shade once it's grown too big to profitably block.