Ok so this happened to me today when I was trying to do The Thane of Voldrune. The Thane of Voldrune - Quest - World of Warcraft Anyway, The guys a pain to kill on that dragon, and he kept killing the dragon and resetting so the last time I got the dragon I flew right up on him to the point that I could have been standing on the ledge with him.
I was stunning regularly but he still killed the dragon before I got him to half health, but when I fell to the ground, my pet stayed up on the platform with the Thane. I had it set to defensive as this was happening, and I didn't get a good screen shot because I didn't realize was was happening until he was almost dead, however I can post one if you want. What was interesting though was that the Thane never attacked my pet, and it just beat away on him until he was dead and the quest was complete.
by Despoiler112