Lightning bolt spam has shown better results. Only thing you really need chain lighting on is trash. Just make 2 Big Button Macros. The trash macro would be your current macro

/assist focus
/run SetCVar("Sound_EnableSFX","0")
/cast elemental mastery
/click MultiBarRightButton1
/click MultiBarRightButton2
/click MultiBarRightButton3
/click MultiBarRightButton4
/run SetCVar("Sound_EnableSFX","1")

Your boss macro would be
/assist focus
/run SetCVar("Sound_EnableSFX","0")
/cast elemental mastery
/click MultiBarRightButton1
/click MultiBarRightButton2
/click MultiBarRightButton4
/run SetCVar("Sound_EnableSFX","1")