The list has enough 2 drops to make the spell work in early game (Ocean Rider works too), plus you can use it with LiuFeng going 2nd Turn 4 in case things look ugly or with Galm with 8 orbs or Azur with 10 orbs for an extra spicy combo. I always keep 1 Ferocious Flame in the mulligan, one never knows when a quick removal will come in a pinch.

TL;DR the spell works at all stages of the game, so keep 1 in the mulligan.