True, hydraulic servo actuators consume about as much power in "throttling losses" (pressure drop) as actually delivered to the load. This all goes to temperature rise of the working fluid. I would judge that hydraulics is the only practical way to even attempt building a powered exoskeleton. I say that because of the power density possible with hydraulics. I can easily carry a two hundred horsepower hydraulic motor but I wouldn't want to put my hand on it when it's running!
Regards,
GtG
At least with hydraulics they carry a large proportion of the waste heat back to the prime mover, where it can be extracted perhaps more efficiently than with the distributed dissipations of electrical actuators.