Annul counters Phyrexian Dreadnought or Powder Keg, since both are artifact spells, so it stops their key threats before they land rather than after. It cannot touch their blue spells such as Vision Charm, Stifle or the counterspells, so don't expect it to do more than answer those artifacts. Thwart is clunky against their counterspell-dense gameplan where you'd rather be proactive with cheap interaction, so it makes room for the extra Annuls. Fire/Ice stays in as a flexible tempo tool. Keep Daze in to tax their Dreadnought or other key spells, and keep Chain of Vapor in to bounce a Dreadnought that resolves. Stasis remains your long-game lock once their threats are neutralized.