What is the macro you are using right now?

The proc is important to utilize (and using it is much easier than other mage procs, like hot streaks and such) ... using it with lesser stacks is only sub-optimal.

You can use one of the gs / lazy macros and blast and barrage normally, with an extra blast 'step' that is a sequence for a blast and missile or blast blast, that will make sure you always have stacks when you let the missiles fly.

So a sequence for classic blasting and barrage and a sequence for blast and missiles ... that you button mash to 'meh' through.

The lazy macro stuff is pretty much as good as it will get.