Solution to Nerf Herald of Ice without Making it Terrible.

I'm worried about the next big patch, since heralds is the only way to a lot of build to have clear as effective as caster builds, so i thought about a good solution to the problem, and it is a simple one:
Make Heralds only work on enemies in your vision/presence, this make heralds very balanced in my opinion, since it won't kill mobs outside your vision.