Honestly, I doubt you can beat the people higher the ones you can't beat. They are higher in the rankings because they are stronger. You could decide to go down in the arena by removing heroes from your formation, runes, and/or equipments. People would win against you, and you would go down in the ranks. This way you could still get to fight more people and steal some stakes. Otherwise, there is no point in being able to fight people who are stronger than the ones you can't defeat.