I agree with the OP that all content should go into DF on the day of its release.

The anonymity of the DF encourages people to participate. Once you participate, you learn and get better which then rubs off on others who are learning. Nobody benefits from limiting the number of people participating in content.

The only reason that the most challenging content is not released to DF straight away is to make the hard core raiding crowd feel special. It's an ego gift to that most ego driven crowd.