Hydroblast and Blue Elemental Blast are both premium answers here, cheaply countering burn spells like Lightning Bolt and Incinerate or destroying red permanents such as Grim Lavamancer and Jackal Pup. This is a pure race against a fast aggro-burn deck, so cut slow, clunky cards like Thwart (effectively a 4-mana counter without a full Island beach) and the non-immediate Flash of Insight for cheap, efficient interaction. Keep Daze and Foil in to protect your Dreadnought from removal, since a resolved 12/12 usually ends the game in two swings before their burn can finish you off. Watch out for Fireblast as a free 4-damage finisher that can snipe you even when you think you're safe.