Melee characters can take Energy Mastery for their APP for additional recovery and/or endurance discount powers. For my non-melee characters with endurance issues, like Storm Summoning, I use recovery serum and the Increase Recovery base empowerment. Beyond that, I look for set bonuses that provide global endurance discounts (Unbreakable Guard, Reactive Defenses, Preventive Medicine, Cupid, etc.) or +Max Endurance, or +Recovery. There's also the accolades that provide +Max Endurance. Those can help too. At 50, Cardiac or Vigor and Ageless usually solves the problem.