If you want to do some serious crafting (like trying to make HQ iLvl70 gear), it's probably best not to queue in the DF whilst doing it. I only ever do crafting to gain levels, or crafting of materials used in higher recipes, whilst using the DF because I don't want to lose rare/precious items. This seems like a sensible thing to do in my opinion.

It's too easy to abuse the system if everything was given back when cancelling. And as has been proven many times before, in ARR and other games, where abuse is possible you can expect it to be used.