Void rays aren't 'overpowered', I think they're just poorly designed overall (too black and white - either useless or dominating). I'd rather see a design overhaul than any buff / nerf.
That's exactly what I like about them, charging up on your base or destructible rocks before you attack I think is an interesting mechanic. I think having to maintain the charge in general is an interesting mechanic. It's similar to catching tanks off guard when they move out and they're not sieged, I like that aspect of the game.