The parry system is in place to prevent the Fireteam from being steam rolled by a button mashing melee Predator, yes.
However, it needs to be altered so that it is a purely defensive option. The parry needs to stun the Fireteam member for the same amount of time as the Predator. He should not be able to retaliate, it should be a mechanic that buys time for your team to move in and assist, not for the Fireteam to single handedly murder the Predator.
If you are the last one alive, then it is time to accept your fate, and become a trophy.
That’s kind of my though on it anyway.

