Not one piece of information on this tread actually does say how the dragon has to be killed or what it does. Unfortunately its all wrong. I am not going to say what it does cast, but its definatly not a mez. I think its best if the guilds attempting this have something of a mystery on this.
I will say this you don't want to focus on killing its friends if you get a bad pull. Also, research from other guilds on how to kill this is probably necessary or you will be sitting for a whole day trying 10 different unsucessful attempts. Study the clues and you may figure it out.
Last comment never believe people that tell you like 6 or even a dozen level 60's can takle a mob like this. Takes a lot more than that.
Icel an Oracle on Druzzil Ro for the Mythic Legion.