I see all the time where peeps put:
/cast [combat] Empower Rune Weapon
Problem is, this makes for a wasted CD most of the time. It will be used, before you even had the chance to consume your runes! Here’s what you should be doing instead for more optimal use, assuming ofc you don’t want it on manual.
/castsequence reset=combat Horn of Winter,Horn of Winter,Horn of Winter,Empower Rune Weapon
This should be the last line in the macro for best results. It basically makes sure you don’t cast ERW until three Horns have been blown first. This means ERW won’t be wasted on trash pulls and won’t be wasted at the beginning of a boss fight.
Note: This works perfectly, but will do nothing at all, if Horn of Winter isn’t in a priority line somewhere above it, like /castsequence reset=0.3 0,0,Horn of Winter.
Let me know if you have any questions about this.