I sort of agree with OP, as an enchanter myself. If anything, I would like to see it as "Sure, you can use my DE services in instances; however, I still get some for myself." To explain it more clearly, say a green in a heroic dropped and you had an enchanter in the group. You click the DE button and you get 5 Infinite Dust from that. What if the enchanter ALSO personally got let's say half of that (most likely rounding down), 2 Dust. In the event only a singular item was produced by the DE, the ratio return for the enchanter would be 1:1. The enchanter would not be able to use the DE button (but could Need or Greed) on the item, and the group could roll off on larger, normal amount.
That, or there is some method to equally distribute the DE'd materials across everyone in the group. Using the same 5 Infinite Dust above, each person gets 1 Infinite Dust. If there are less materials than people in group, then you roll off like you currently do in a dungeon and then the top X rolls win 1 Dust each.