Force of Vigor is a two-for-one blowout against Aluren, able to destroy both Aluren and Omniscience in one card, and can be cast for free by exiling a green card when it's not your turn. The extra Swords to Plowshares answers Atraxa, Grand Unifier before it can bury you in card advantage. Shadowspear and Outland Liberator are too narrow against a deck with few relevant artifacts/enchantments to destroy outside Aluren itself, and Sylvan Safekeeper's protection is less valuable against a combo deck that isn't trying to kill your creatures with removal.