500 feet is hardly a weakness. Most fights won't occur at such ranges with ANY kind of magic anyhow. Remember that a weakness is not a weakness if it never comes into play.

Line of sight would be great, but because Psychomancy's effects are instant that means you can't think 'oh shit, better duck behind a rock'.

Limiting it with penalties for multiple actions at once matters little: They only need to affect one person to get you. 

Making it take time to affect is exactly what I'm pushing for.

Psychomancy has been given a large amount of power against the unwarded in the hopes of making it feel stronger and avoiding making one feel useless. I can guarantee I've felt useless a lot more often than Elite has, and a great amount of my frustration comes from how 'easy' Psychomancy seems. Even if he doesn't abuse it, the knowledge that Ssarak or any Psychomancer CAN abuse Psychomancy while I have no such thing feels awful. We need to make Psychomancy FEEl less frustrating to fight against. 

I can imagine making someone have Seizures with electromancy but the amount of control required to 'zap' immunity into herself without breaking things would take more training and detailed knowledge of the biology of her brain than Alaira is reasonably capable of.