Omni-Tell's whole plan is Show and Tell putting Omniscience into play to chain free spells into Emrakul, the Aeons Torn or Atraxa, Grand Unifier, and Force of Vigor destroys up to two artifacts and/or enchantments, directly answering Omniscience. Veil of Summer protects your interaction from their Force of Will and Flusterstorm while punishing their blue-heavy draws. Grafdigger's Cage does nothing since their threats are put into play via Show and Tell rather than the graveyard, so it comes out for proactive answers. Keep Wasteland and Boseiju, Who Endures, since Boseiju's channel ability is another way to strip Omniscience or a City of Traitors before they combo off.