Unholy Heat is a premium answer here, killing Dragon's Rage Channeler, Monastery Swiftspear, and Slickshot Show-Off for one mana, and dealing 6 damage with delirium, which is easy for us to turn on. Thoughtseize is too slow against a deck this fast and proactive, and the 2 life it costs matters against their burn. We want maximum cheap interaction against their low-toughness creature swarm, so Unholy Heat takes those slots. Grafdigger's Cage stays in the sideboard: it would shut off our own Nethergoyf escape and Detective's Phoenix being cast from the graveyard, and it does nothing about Cori-Steel Cutter's Monk tokens, which are created directly on the battlefield.