for arcane, to maximize DPS this is the rotation you should use in most fights:

3x arcane barrage
if missile barrage proc'd, cast arcane missiles (to clear buff)
else cast arcane barrage (to clear buff)
<rinse and repeat == use arcane power and trinkets every cooldown, use evocation when icy veins and/or bloodlust is almost over>

for multiboxing macros you can either have 3 buttons and rotate between 1,1,1,2 or 3 :
#showtooltip
/cast [nochanneling] arcane blast
(same for arcane missiles, arcane barrage)

or you can use one single castsequence and get about 90% of the DPS:

#showtooltip
/castsequence [nochanneling] arcane blast, arcane blast, arcane blast, arcane missiles

You actually don't end up losing a lot of DPS by using AM even if missile barrage hasn't proc'd. You do however lose DPS by missiling too early, wait until you have 3 stacks of the buff then AM to kill the buff. If mana is an issue (esp since evo/gem management is hard when multiboxing mages) you can drop to 2x AB's then 1 AM, but your DPS will suffer a bit.

There's no reason to really ever cast scorch or pyro in PVE as an arcane mage, you are betting off POMing a arcane blast since it can trigger arcane bonuses. In PVP of course you may want to POM a pyro to burst someone down.

Moog, I'm a little confused why you have both arcane and scorch in your macros. Scorch only increases critical chance against enemies if you talent into improved scorch, and an arcane mage can't have both IV and imp scorch. So glyph'ing for imp scorch and casting it does nothing for your party. IV is a much higher DPS boost than spec'ing for scorch, even taking into account a caster team.