Dimir Control has no red cards and its only artifacts are Baleful Strix and Mukotai Ambusher, so Hydroblast and artifact-hate style sideboard cards have almost nothing to hit. Duress strips a key Counterspell, Snuff Out, or Cast Down before we commit our threats, which matters against a deck built to grind with permission and removal. The extra Nihil Spellbomb copies are low-impact graveyard hate against a deck with no real graveyard payoffs worth attacking, so a couple can be trimmed for proactive disruption. Keep the core artifact threats at full count since this matchup is about resolving our clock through their removal and counters.