Dimir Midrange is a grindy blue-black control-ish deck with Psychic Frog, Orcish Bowmasters, and its own Counterspell/Force of Negation suite, so Mystical Dispute is often a two-mana or cheaper counter against their many blue spells like Preordain and Quantum Riddler. Consign to Memory answers their triggered abilities from Orcish Bowmasters and Psychic Frog's card draw trigger indirectly by countering the colorless Mishra's Bauble-style effects and any triggered abilities they rely on. Wrath of the Skies is weak here since they run few small creatures worth sweeping and it can be blown out by their countermagic, so trim it down against a deck with little board presence to punish. Orim's Chant is also too passive in a matchup decided by resolving your own threats through their counterspells, so replace both with proactive countermagic; keep Narset, Parter of Veils and Teferi, Time Raveler in as premium pieces that shut off their card selection and protect your own spells from countermagic.