@JohnnyUSA You do not need an addon to do everything for you.
@kas Here is your macro:
/script if not IsCurrentAction(#) then UseAction(#) end;
/cast Sinister Strike(Rank 8);
* (#) corresponds to the action bar number
* you put your autoattack into a slot on your action bar then enter the number for the slot into the brackets
* web search "wow action bar numbers image" to find the number for each action slot
gl