Before revision:  Counterexamples are found in models of molecular motors, of circadian cycles and of sensory adaptation. There, performances or efficiencies are not always monotonously increasing with the dissipated power. The simple general reason is that nondissipative and time-symmetric kinetic aspects are also relevant for establishing optimal functioning.
After revision:  The simple reason is that nondissipative and time-symmetric kinetic aspects are also relevant for establishing optimal functioning.