I have left my stats and gems and enchants as they were.
Some people say crit over mastery and others vice versa.
Hey Q, the one thing I would suggest is that if you are planning on going Destro full time, I would swap out your legendary meta gem for a Burning Primal Diamond. For Destro, this is a much, much better choice and is a dps gain over the LMG. Whenever I play Destro and am able to reforge before a fight, I use a separate helm with the Burning Primal in it.