Skill gems for Storm mages

I was looking for skill gem recommendations for my storm mages.

I am currently using

Feeding frenzy
Arcane tempo
Muster
Lightning mastery
Minion Mastery

I have 521 spirit running 12 storm mages with 5 other persistant minion types.
I am only using them for there basic attack (635-12018) which chains 5 times.

Was wondering if there are any good gems I have missed that could use to boost the damage further.

In case anyone is browsing this in the future.

I finally gave in and picked up the boots to get the 20% reservation reduction, the loss of speed really sucks.

I replaced the 2 +level gems with Elemental focus (giving up shock) and controlled destruction (giving up crit).
I made another storm mage skill gem for lightning resistant bosses with shock and exposure setup to switch a couple of the mages too when needed.

I also got my resistances up to the point where I could try out an evergrasping ring.

I am now running with 17 storm mages each hitting for 1024-19317 every 0.77s.

Maps are much easier but the boots not having speed really does hurt.