Ruby Storm wants to chain cheap rituals and cantrips to reach a lethal Grapeshot or Past in Flames turn, so Damping Sphere taxes each successive spell they cast, making it very difficult to chain enough spells together. Pithing Needle can shut off a key repeatable ability if they rely on one post-board. We're not looking to race them, so we trim slow top-end creatures for proactive disruption while keeping our mana base and core creatures intact to pressure them before they assemble a storm turn.