Question: Throughout various episodes, the augments have shown themselves to be very strong, yet whenever they face each other they easily succumb to whatever physical violence is directed towards them. Why is this?
Answer: Two augments fighting each other would most likely look to an outside observer as a fight between any other two people. The augments would be fairly evenly matched (allowing for an individual's weight etc) and so could take each other down the same as normal people fighting.
Chosen answer: They're stronger than humans, but they're not invulnerable.