@Nick

"the only profession that can use the dust is the enchanters and they are the only ones having acces to it."
I know tailors, for sure, use dust so there is AT LEAST one other proffession that can use the mats. Besides, its not like the post said this option was being made available on EVERY item you pick up that could be DEd...only ones in dungoens. So Blizz is basically ensuring that people who PuG with a group that has no chanter can still have the dungeon loot DEd as if they did.

"why am i not alowed to complayin about ahs going to be flooded with cheep stuff "?
Complain all you want, I'm just saying I don't see it happening like that. MOST stuff in heroics is DEd already so the situation there isn't changing. Some people keep the mats they get for their own use, some sell them. Personally, I ask only to roll on an abyss if the end boss loot is DEd. Otherwise I let the chanters keep the shards for any loot they DE and I pass on greens that drop if I know we have a chanter in the group. I don't see how this creates a "flood" of chanting mats on the AH.

Besides, the blues and purples don't DE into dust, do they? Just shards, I thought. My impression of this is that it was applicable only to boss loot. Now if that option comes up for greens that drop, as well, then I guess that you have a point there, as well. I still dont see how it creates a flood of the AH though.