I did a search using the the keyword Oculus but i did not see this anywhere.
first off you start on normal and you kill up to the boss where you get the drakes. You get your Drakes and continue on...but leave one construct group alive if you kill them all this wont work. Then you fly up high enough to die when you dismount you must hit a platform. when everyone is out of the instance change it to heroic. when you log in you will have your drakes and can kill the last group of constructs and take out that remaining bosses shaving a good 10 minutes off the time it takes to kill him for the achievement.