Mods such as Autogive help to some extend, as they display a message when your ACU is taking damage. The difficulty with this is that it's very difficult to distinguish between damage that you already know about (eg, you're dueling with another ACU near there) and the "silent killers" of Cybran or Seraphim T2 PD. Usually by the time you realize there's PD there it's too late to pull back.
Now, I know this can be fixed by scouting. Everyone should scout and scouting is good and great. We know that.

My proposed solution is to add a new projectile weapon to Cybran and Seraphim PDs. It would do no damage; it's purpose would be for visual purposes only, as it would then be visible both zoomed in close with it's visual effect and zoomed out with the yellow projectile weapons fire dot. If we want to make it look "pretty" then it could theoretically be an energy pulse moving along the beam.