This wouldn't work when operating in conditions their body isn't accustomed to; you can't have an athlete perform well at high altitudes when their brain and muscles aren't used to low oxygen levels, areas with high or low moisture content in the air if their lungs aren't ready for it or a wide range of temperatures and environmental conditions that would devastate even the most well trained and healthy soldier if they come from and trained in a vastly different climate.
I saw the biggest problem with power armor explained decades back on an early website about military technology about why it isn't suitable, it's the weight per mass not power requirements. When there's several hundreds pounds pushing down on the ground in a very small footprint that makes it impossible to use in any slightly difficult terrain. In urban environments you'll barely be able to squeeze through doorways or go up/down stairs.
Also one of the biggest issues for designing bipedal robots is the ankle joint and I'm sure it'll be the same for power armor, what good is it if a cheap mine or grenade booby trap could make it immobile? The Achilles' heel myth has lived on for millennia because it's true in spirit.