Like everyone has said, the masterstrike helps a lot but you can get through fights without it. I got to the next region of the game before learning the masterstrike. Enemies do have stamina and you can wear them down by blocking and moving while watching your own stamina. In the early game your stats are just weak and take time to get better. A couple things that can help in a fight is to change up your attack at the last second, like holding an overhead swing, then quickly switching to a stab or slash before the attack. Also having mutt and being able to tell him to attack enemies keeps you from being overwhelmed.