Reason: This suggestion is thought, initially, to balance Tier 3 equipment in low areas and avoid one-hit kills from some equipments with high burst power.
What is Sonic Mode? > http://www.youtube.com/watch?v=G5tq7EOXDKg Basically, unless you are under 1 bar of health, you can't die usually. That's the basic rule of thumb.
How this would work in enemies? Basically, when hitting 10% of their health they would get knockbacked and enter invincibility mode during it - remember, invincibility effect is shown as a purple spark with the "shield" sound effect. When they get up, then they will be able to be eliminated normally, unless a healing mob - Mender, Silkwing... - gives them more health over 10%, which will then enable back their Sonic Mode.
That is it... a simple suggestion this time.
It would certainly be a reason to not vomit damage everywhere mindlessly.
It would create yet another reason to target medics first, though anyone competent would know to do so anyway in a "warzone".