Dimir Midrange is a grindy matchup full of card advantage and disruption (Thoughtseize, Narset, Parter of Veils, This Town Ain't Big Enough), so Duress helps you proactively strip their interaction before deploying your own threats. Invoke Despair is a powerful value swing, forcing a creature or planeswalker sacrifice (hitting Graveyard Trespasser or Narset, Parter of Veils) while drawing you a card if they can't comply. Trim Sentinel of the Nameless City and your own Graveyard Trespasser, which trade symmetrically with the opponent's copies and add less value in this long grindy matchup compared to the raw card advantage Invoke Despair provides. Keep Sheoldred, the Apocalypse as your premier threat since its life-drain triggers punish their card-draw-heavy plan.