The key card is present but its support is thin.
Prioritize useful support such as Dockworker Drone or Drix Fatemaker.
Give an existing attacker a counter with Drix Fatemaker or Enhancer before combat. Fatemaker supplies trample so a small blocker cannot stop every point.
Your deck already enables the plan but is losing the early turns.
Take a castable early creature or efficient answer before a second expensive payoff.
Haliya needs two white mana. More counter payoffs do not replace early bodies or the sources needed to cast the five-mana legend.
The support is missing
Favor independently useful creatures and interaction if the narrow support does not arrive.