Dimir Midrange is loaded with blue spells (Counterspell, Preordain, Quantum Riddler, Subtlety, Tamiyo, Inquisitive Student) making Mystical Dispute a premium answer at just {U} against their counterspells and card advantage engines. Into the Flood Maw bounces Orcish Bowmasters or Psychic Frog before they snowball value. Veil of Summer is redundant with your existing hexproof-granting plan against their black/blue disruption suite (Thoughtseize, Fatal Push, Counterspell) but four extra pieces of interaction matter more than the marginal fourth Veil, so trim to zero copies; Disciple of Freyalise is too slow and easily answered by their many instant-speed interaction pieces like Counterspell and Subtlety. Keep Pact of Negation and Endurance, since Endurance answers their Psychic Frog graveyard activations and provides a free flash blocker.