Jeskai Control wants to assemble Tablet of Discovery and Jeskai Revelation value engines backed by counterspells like Spell Pierce and It'll Quench Ya!, so proactive Thoughtseize lets you strip their key piece before they stabilize. Their early interaction for your creatures is mostly burn like Firebending Lesson and Combustion Technique, plus Divide by Zero, which can bounce a creature or a spell. Fable of the Mirror-Breaker gives you a Goblin Shaman token that makes Treasure and some card filtering, and once it resolves it is out of reach of their counterspells. Cut Biotech Specialist since it is a slower, less impactful body in this matchup, and trim Lively Dirge since you'd rather hold up proactive threats and disruption than invest extra mana recurring small bodies.