Aggro radius

I was doing a quest which requires me to kill sal'guk Ogres,which are found on Abandoned Isle. Upon getting there I found that they were around lv38,or the ones that I saw were,as my dragon ws lv30 at the time,but I decided to try one and see how it went,but first I needed to wait for a few minutes for my death penalty debuff to wear off,so I backed down to the first tunnel entrance and went to grab a drink and go to the bathroom. Upon getting back I found that one had aggroed all the way down the corridor and killed my dragon. Is this usual for them to aggro when they can't see me,and over such a large distance?

There always were 1 or 2 ogres patrolling along the outside mountain path.

But do they patrol right down to the tunnel leading up? As That's where I was and that's a big patrol radius..