Izzet Aggro is a prowess-fueled burn deck, and your 1-toughness Elvish Mystic dies to virtually everything they play, so Setessan Petitioner's extra toughness and devotion-based life gain is a much better use of the slot. Arasta of the Endless Web blocks their ground creatures profitably and punishes their spell-dense turns with a steady stream of 1/2 reach Spider tokens. Leyline of the Guildpact doesn't keep your creatures alive against burn removal, so it's a low-impact include here compared to more resilient bodies. Keep the ramp core since Izzet Aggro has almost no way to interact with a resolved Cavalier of Thorns or Storm the Festival finding multiple permanents.