are you gonna ignore missile barrage procs or you using a notifier for them. miks scrolling battle text is good for that. also ive not done much research but it seems as though the standard rotation is
Arc Blast, Arc Blast, Arc Barrage
OR if Missile Barrage procs during that, you change it to
Arc Blast, Arc Blast, Arc Blast, Arc Missiles

i was only arcane for a minute at lvl 71 so im not sure but might be better