As the topic states, tried that today me and a friend (he was the lock).
All you need to do is put pet (we used imp as in the video) but I'm pretty sure you can use what ever pet, as long as it's positioned closer to boss than you guys are.
BUT pet should NOT be in meele range of the boss.
Have the pet attack first and that's it, pet wont take any dmg and will still remain 100% aggro even if u nuke.
Dunno if repost but if it is then I apologize.
video of lock doing this exploit:
This is a solo vid, but as I said it's possible to bring more friends, or just have tanks go dps for even faster boss.
Enjoy.