1. Everyone from your heroic group go to Mannoroc Coven in Desolace
2. Queue for a heroic from there
3. When you are ready to kill a boss, teleport out of instance. Kill 5 demons and you get a buff which increases your crit by 25% and regens 5% of your total health every 3 secs, lasts 1 minute.
With this buff some of the harder heroic achievements should be a bit, if not significantly easier.
http://i.imgur.com/XwAdL.jpg
http://i.imgur.com/bKUwm.jpg
http://i.imgur.com/4oMoi.jpg