Pyroblast is live against their blue cards like Force of Will, Daze, and Brainstorm, letting us protect our own threats, and it can destroy a blue Murktide Regent if they land one. It does nothing to their red cards such as Dragon's Rage Channeler. Deafening Silence restricts them to one noncreature spell per turn, which slows down their cantrip chains that fuel Delirium on Dragon's Rage Channeler and growth on Murktide Regent, though it also limits our own noncreature spells so it's a narrow, situational inclusion. Cabal Therapy is weaker here since Izzet Delver plays a low, cheap curve of cantrips and burn rather than a small number of key cards worth stripping, and their hand refills quickly. Goblin Bombardment's sacrifice outlet is a lower priority than keeping our proactive clock and removal online against their fast, interactive gameplan.