Amulet Titan relies on Urza's Saga for Construct tokens and value artifacts, so Wear // Tear can destroy it or another key artifact/enchantment like Amulet of Vigor outright. Spell Pierce is a reasonable deterrent for Scapeshift but is a fairly low-impact single swap, so we keep the plan minimal rather than overhauling it. Your Stubborn Denial and Spell Pierce remaining in the configuration still punish their Scapeshift and Primeval Titan plans since Ferocious is easily live with Territorial Kavu. The matchup is largely a race, so keep your proactive threats and mana intact rather than diluting the deck further.