Tron wants to ramp into Expedition Map, Ancient Stirrings, and big threats like Maelstrom Colossus and Bramble Wurm, so we want to race or disrupt their mana rather than attack their hand one card at a time. Avenging Hunter's trample and taking the initiative gives us a proactive threat and card advantage engine to close the game before Tron assembles its full mana base. Undergrowth Leopard can sacrifice to destroy an Expedition Map or Bonder's Ornament, slowing their ramp plan. Mesmeric Fiend and Quirion Ranger are cut since hand disruption is weak against a deck with so many redundant ramp pieces and Quirion Ranger's utility is marginal here.