That's just not how it works. Empowerments increase the damage of Lunar Strike and Solar Wrath. Our mastery directly increases the damage component of those empowerments. Crit does nothing but increase our chance of getting a critical strike. It's dynamically updated while mastery isn't because mastery procs would be worthless if they didn't snapshot with that buff. It's probably unintended for Balance Druids to be able to snapshot mastery outside of the proc and it'll most likely be fixed soon enough.