Electromagnetism not proccing from Mirage Archer

There is nothing in the Electromagnetism support gem's description that suggests its effect will not work if the skill is not used by yourself.
However, using Mirage Archer with Stormcaller Arrow and Electromagnetism slotted, the Electromagnetism effect will not proc even if there are more than 3 enemies shocked closed together.

Mirage archer and other proxies can't trigger skills generally.