The ruler of the Highgate quest bug

Maybe i just miss something and i'm not sure this is right place but any way. I have been trying to complete Ruler of the Highgate quest but Sekhema Feather don't seem's to drop at all I killed boss 2 times then gone and did all quests optional quests before that one and redo quest (killing Kira and Garukhan) i made sure to check if maybe it is miss placed but only can find white / blue / yellow items that bosses drop no quest item. Is it bug or i missed something?

I'm having trouble finding Oyun and Kira in The Quarry, I've cleared the entire area, not here...

@Kettani: Oyun and Kira are in the Arena part of The Quarry