If you have mana problems, put the arcane blast sequence like this:

/castsequence [nochanneling] arcane blast,arcane blast, arcane blast, arcane blast, arcane barrage

that way you wont cast more than 4 arcane blasts in a row.

Only downside of this macro, is that its very luck dependant, and DPS will fluxuate a lot. If you consistenly proc arcane missiles after 1-2 arcane blasts, you wont benefit much from the stacking buff that arcane blast gives you. I had some tests on the dummies, and one time, I got a near perfect proc rate, just about every 4th AB, id proc a missiles, and I did like 9k DPS (including one 42k crit...) and another time, I got the proc too often, and only did 5-6k dps. Other times, I wouldnt get a proc very often at all, and i'd run oom very quickly. I had to switch between molten armor and mage armor as my mana dropped.

I also tried fire mage, and we still have the issue of Pyroblast procs. If they made pyroblast work like arcane missiles proc, it would be a cinch, but as it is now, you only want to be casting pyro when it procs, otherwise its low dps. Maybe Frost isn't so bad now?

As for mirror image, I've found that these types of macros only work when one spell that's not part of the sequnce (not counting the buffs that arent on the GCD like arcane power, etc. Best way around it is to have a second button for starting a boss fight.