Parry a "core mechanic"
So, the most recent bug fix list put out by Kabam called parry a "core mechanic." I feel very certain that almost every player runs with parry in their masteries. You can't play the game without it these days.
So this begs the question -- why does it cost us a mystery point at this juncture. Further, dexterity is the same way. If masteries are "core mechanics", then they need to be removed from masteries and altered to interact more effectively with things like mystic dispersion.