You're talking about muscle mass that means someone with huge muscles like Bruce should be able to hit harder and take hits better than someone slender with less muscle mass, such as the female martial artists you mention, but martial arts isn't about just hitting or tanking.
Various martial arts are designed so you can take down opponents that are bigger and denser than you, like judo throw taking advantage of the opponent's weight, kung fu moves that aim to strike at the enemy's weak points like the neck, or jiu-jitsu that redirect an opponent's strike back to themselves.