you can also add mouse over
/ac "Nascent Flash" <mo>

i copied one of the internet and modified it slightly,it looks like that:
/micon "Nascent Flash"
/merror off
/ac "Nascent Flash" <mo>
/ac "Nascent Flash" <2>
/ac "Nascent Flash" <b>

it goes for <mo> mouse over, if there is none > 2nd party member <2>, if there is no party member > it goes to companion <b>.
i forgot what <b> stand for exactly,but its basically for chocobos or other allies when you do solo instances with some sort of npc, so it will be applied to one of those too.