Dimir Control runs almost no creatures, so Vicious Rivalry and Pick Your Poison's sweeper modes are largely dead weight; trim them for more countermagic. An Offer You Can't Refuse counters key noncreature spells like Deadly Cover-Up or The Theorist, Jace Beleren, and Annul can stop a problematic artifact or enchantment if they bring one in. Flashfreeze stays in the sideboard since Dimir Control has no red or green spells for it to counter. Lean on your existing Spell Snare suite and card advantage from Awaken the Honored Dead to win the long grind.