Am I able to farm for legendary crafting materials on Normal difficulty, or must I be on Torment (1-6) for these to drop? Here is a list of the materials I mean: http://www.diablofans.com/forums/diablo-iii-general-forums/diablo-iii-general-discussion/83094-guide-legendary-crafting-materials-drop-locations
Yes they can, but the chance is not good.
In the 2.0.4 patch, this information was posted:
The drop rate for death breath as posted by a blue on the forums are as follows (source):