Dimir Excruciator wants to grind with discard, countermagic, and card advantage engines like Uldaros Theorix, so proactive discard with Duress strips their removal or counterspells before they can protect their threats. Rottenmouth Viper is expensive and clunky against a deck full of cheap interaction and Deadly Cover-Up, while Stir Up Trouble's conditional cost is awkward when they have few must-answer early creatures. The extra Requiting Hex is a narrow, cheap answer: it can only destroy creatures with mana value 2 or less, so it cannot hit Seasoned Cryomancer (mana value 3). Its real targets are an animated Restless Reef and the Illusion tokens from The Theorist, Jace Beleren. Superior Spider-Man and Overlord of the Balemurk still need answers, so don't lean on Hex for them.