GoS Hates Divines
One of the little known secrets of the game is this:
The Guild of Shadows monsters HATE Divine monsters!
In the GoS offs from The Shadow's Embrace it is possible to take advantage of this fact, and essentially power level yourself. An off location such as Guild of Shadow's Training Chamber of Doom has two types of mobs: Divine Angels, Knights and Reavers, and their Guild of Shadows counterparts. If you run through the dungeon normally, you will encounter them one at a time, fight them one at a time, and it will be like any other dungeon.
BUT, here is the trick! Use the "herding" monsters technique. Run through the first three or four groups you encounter (these are usually Divine) until you begin meeting the other type (Shadow). Pull these groups back to meet the first ones. If you have roughly equal numbers of Divine and Shadow, they will now DO BATTLE WITH EACH OTHER! You can duck over into a corner, and just watch the fight. The great thing is that every time they kill each other, YOU get the experience points!
Usually one group will eventually wear down the other. You can go ahead and fight them yourself, or you can just repeat the whole process by drawing more of the opposite type in. All the loot that drops is yours.
This can work really well for a group. Each member of the group runs to a different area of the dungeon and ALL the mobs from the entire dungeon are pulled into the middle to fight it out!
Using this method you get about 1000 xp when all the mobs wipe each other out. Just reset and keep the xp counter spinning for as long as you don't get bored.