Dismember cheaply answers their key threats like Stoneforge Mystic, Recruiter of the Guard, or Overlord of the Balemurk before they generate value, even paying life when needed. Veil of Summer protects our combo from Thoughtseize and gives hexproof from black removal while punishing their black spells. Their deck already runs Karakas and Wasteland to fight our lands, so keeping our full mana engine (Urza's Saga, Thespian's Stage, Wasteland) intact is critical rather than diluting with narrow artifact/graveyard hate that doesn't line up well against their white-based creature shell. Maze of Ith is cut since it only stops a single attacker against their wide, evasive creature suite.