Lifegain's whole plan revolves around triggering abilities off gaining life with Case of the Uneaten Feast, Amalia Benavides Aguirre, and Ajani Resolute, and Duress proactively strips their key enablers or removal before they can stabilize. Strategic Betrayal makes them exile a creature of their own choice, so it won't reliably hit their best threat, but it also exiles their graveyard, denying recursion from Moseo, Vein's New Dean, and it forces them to give up a body against a deck that wants to keep developing its board. Forsaken Miner's inability to block is irrelevant on offense against their small lifegain creatures but it trades poorly in a long grind, so we cut it for more proactive disruption. Dissection Practice's minor life swing is negligible against a deck built to gain far more life than we can offset, so it comes out for Strategic Betrayal's graveyard hate and edict effect.