The warrior-troubadour would rule the world
This mastery approach you describe has three limits. The first is the obvious strength and stamina tests that KillingTime mentioned in a comment. The second is their own imagination for the creation of an imagined action to do. An individual that cant think beyond, "Ogg stole my stick. Make Ogg's head have 2 more lumps than it used to." will rapidly find their creativity is too low to permit striking the more creative individuals, who have taken the time to shape more efficient ways of defending themselves. This leads to the third limit, the imagination of others. Creative use of a spear can accomplish a great many things if one is nimble and quick, but once someone has decided to engage in a defensive action, your options to strike with become limited.
Accordingly, those at the top of the "food chain" would be the warrior-troubadours, the warrior-poets, and their kin. They would have the imagination to figure out how to use that perfect mastery to accomplish ever more nuanced goals, as they refine their arts. In our earlier example, if Ogg has already begun working with the stick to protect himself, he'll probably find a way to take 2 lumps... but small ones. And, in exchange, he might disarm his opponent, and maybe even woo his opponent's wife away with the beauty of his actions. Lose your wife to a warrior-troubadour once or twice, and you'll learn not to try to put lumps on their head very quickly.
Creativity could literally rule the world.