This is where I've got to so far with it and works quite well. The dps loss I can see is when missiles proc just after the arcane barrage dump.

Button 1
Code:
#showtooltip
/stopmacro [channeling]
/castsequence reset=target nether tempest,null
/castsequence reset=target Arcane Blast, Arcane Blast, Arcane Blast,arcane blast, arcane blast,arcane barrage
/use 13
/use 14
Button 2: Arcane missiles, Button 3: arcane power, button 4: mana gem button 5: mirror image, button 6: presence of mind.

all in 1 key.