If what you need is dust.... one of the best places for it was in a thread right below yours:
Here
Out of the Temple of Ages, run to where the Fog Nightmares are, the green circle.
The shadowy remnants turn into dust as well. You might want to save them fro Wintersday. They are one of the collectors items you can use then.
You can also farm it with a warrior. I do not kill the boss, so Pain Inverter can be replaced. I am sure the build can be tweaked. A run takes about 15 minutes.
[warrior/rit;OQgkERVXILqkFj3ExjcZGTAwgVXB]
Enjoy!