Ok so not sure how to start this out. But I will say this is more a clever use of mechanics more than it is an exploit but can verify that it does in fact work and I hope you all enjoy it.
What you will need:
1 Priest (shadow spec'd)
1 Any other class (I prefer using a rogue)
What you do:
Zone into Bastion of twilight. Set the difficulty to 10 or 25. 25 man is the best for gold drop reasons. Ok go in and have the rogue (if you have a rogue) sap one of the first pulls mobs. then simply have the priest MC another of the targets. Walk the MC target back behind the priest and let the other mobs Beat on it.
Now here is where you will need good judgement and timing. When the mob has about 100k health left maybe a bit less. Have the priest release the MC and Dispersion Right away (A macro for this is best). Once the low health mob is released the other person finishes the last 100k health off the mob killing it then books it out of the instance. With a rogue they simply hit vanish. the priest will die so being naked as a priest is advised.
The priest will release and run back and the mob you killed will be lootable. Each mob in here on 25 man drops between 15 and 20g per mob. Not to mention I found an average of about 3% drop chance of epic BoEs.
The downside to this is it does take some time to master. But it is VERY important to note that the secondary player MUST do about 100k damage to the mob before it dies to get loot credit for the both of you.
Rinse + Repeat = Profit.
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Couple of things to note:
You'll want to have the secondary person that will be finishing the mob to be in combat so that the crossfire mobs can drop shadow trap things on that person as well. A shadow trap on the priest to soon into the MC and it's bad news.
The priest should also be aware things like Psychic scream will work on all the mobs minus the soulblades so if they leave their gear on they can Scream + Dispersion and still make it to the exit in time in thus not die every pull.
If using a rogue, DO NOT VANISH until the mob is dead.