That must have changed in the last 3 years as I was subscribed until early 2011 and the only way to activate a killer effect was to be the actual target, not high on the enmity list. Though if I recall the Killer effect also originated as a small haste/damage buff that was later changed to an intimidation for fear of unbalancing DPS jobs at high levels. If it's the FFXI rendition of Killer effects I don't see it being added or useful in the instance it is.