How should I balance Mastery and Crit?
Your first focus needs to be spirit right now.
You're sitting at extremely low spirit. If the piece does not have spirit on it- reforge it into spirit (your shield and leggings for example).
Gemwise: Intel/spirit hybrids (I want to say it's a purple gem- can't remember off the top of my head) into red slots, pure spirit into blue slots, there's also a mastery/spirit green gem for yellow sockets.
Work on your reps also (the new island dailies have 476 gear)- don't just buy the pvp gear and not reforge into spirit. If you have justice points, the justice point gear does not have a rep requirement.
After that, focus on mastery or crit. Spirit has to come first though. Personally, I would advise on lowering your haste right now: until you have a decent balance between spirit, mastery and crit. At your gear level, I don't advise that much haste- you don't have the mana regen to support it.