Dimir Midrange has a glut of removal, counterspells, and tempo plays (Requiting Hex, Bitter Triumph, Kaito's -2, We Say Thee Nay!), so Surrak, Elusive Hunter is valuable both as an uncounterable trampler and because it draws cards whenever opponents target your creatures with spells or abilities. Torpor Orb turns off the enters-the-battlefield triggers on Floodpits Drowner's tap/stun, Dream Beavers' drain and scry, Spyglass Siren's Map, The Wondrous Wasp, and Tishana's Tidebinder, which meaningfully slows their tempo plan. Earthbender Ascension and Shared Roots are cut since they're too passive against a deck full of efficient interaction and card advantage that will simply out-value a slow landfall plan.