It Appears the "Augments Killer Effects" Enhances quite a few things.
its about ~+2% Damage to the mobs you have Killer against, and it appears "Enhances Killer Effects+" Gear Enhances the bonus of the "augments killer effect" body as well.
I.E Killer Effects+1 Gives about another 1%, Making Merited Killer Effects essentially 5%DT against mobs you intimidate.
On top of that it appears (The body alone) Gives a -DT effect as well to mobs you intimidate.
I.E: 1000 needles will do ~490 with 2 people in range, 980 with you alone, its a small DT but a DT non-the-less.