Dimir Midrange has a heavy removal and counterspell suite (Spell Pierce, Spell Snare, We Say Thee Nay!, Bitter Triumph) plus card advantage engines like Enduring Curiosity and Kaito. Duress strips a key counterspell or removal spell before you commit your threats, smoothing out their interaction. Guerrilla Gorilla is a reasonably sized reach creature that dodges their small removal suite less well but adds pressure; more importantly it thins the slower value cards like Fanatical Offering that need bodies to sacrifice when they're removing your creatures early. Keep the core sacrifice engine intact since it out-grinds their card advantage over time.