Game balance is something we constantly work on with Battle Legion. Unit, player and army specific data is regularly analyzed to see how units and players are performing, and we make changes when they are warranted. In some cases, a certain unit might seem to weak or overpowered, this is most likely something that we have already considered and a strategy/gameplay solution is available to remedy the 'imbalance'.
We also change game balance routinely with new Seasons bringing changes to units and new Powerstones, new Ranks introducing new units, and Eras changing the Powerstone pool and game balance more extensively.