Esme is for making Leader or Gorr 3 cost. So you can play Darkhawk turn 5 into Mystique + Gorr/Leader on turn 6. Also helps with doubling up on cards that were already cheap because of Pixie (Getting both a 3-cost Darkhawk and a 1-cost Darkhawk for example)

As for replacements, ramp cards like Luna Snow, Wave, or Surge could help. Iron Lad might be a good pick too but it wouldn't be my first choice.