In Patch 7.3 Notes (Preliminary)
Quote Originally Posted by 7.3 Patch Notes (Preliminary)
The following additions and adjustments have been made to Phoenix Down:
  • Can now be used on players outside of your party.
  • Can now be used in combat in public areas.
  • Can now be used in combat while undertaking certain types of duties:

    Available Duties
    • Instanced Dungeons
    • Guildleves
    • 4-player Trials
    • Treasure Dungeons
    • Deep Dungeons
    • Field Operations
    • Variant Dungeons

    Any duties with restrictions on Phoenix Downs will now display that information in their Duty Finder description.
    * This restriction does not apply to the guildleve "Solemn Trinity" and the trial "The Great Hunt (Extreme)."
These occurrences should read Guildhests / guildhest.