Players wearing anything from the Wyrmal Abjuration Set have the hidden effect of Dragon Affinity, therefore they can be intimidated by monsters or other players with Dragon Killer. This may present problems with Dragoons (or players wearing Dragon Killer gear) who are trying to be cured by anyone wearing the said gear.
Dragoon Wyverns are also considered part of the dragon family and can be intimidated by Dragon Killer. A Dragoon Wyvern's job is that of DRG, therefore strangely enough they possess the Dragon Killer trait themselves.