High Noon is devastating against Amulet Titan's one-spell-per-turn ramp plan, denying them the ability to chain Arboreal Grazer into Amulet of Vigor into land drops and Scapeshift pieces in a single turn. Thoughtseize is weak here since they're a ramp/combo deck with land-heavy hands and Primeval Titan copies that don't care about discard disruption once they resolve. Mystical Dispute cheaply answers their blue spells like Scapeshift's search isn't targetable, but it can counter Summoner's Pact or other blue instants/sorceries they might have. Keep Thoughtseize count low; prioritize disrupting their engine pieces with High Noon and your proactive creatures.