I played a lot of mobile games with PVP and those that have a time limit will make you win if your total hp is higher than the enemy or you have more units than the enemy team. I think this should also be implemented in this game as well. When you have 5 remaining people and only 1 enemy left that should be counted as a win. Or you can add a buff where everyone's damage becomes bigger and heals will be less the closer it is to the end of the timer.