PVR, I'm afraid I have to disagree. If the conscience of the representative goes against the majority of constituents and he votes contrary to that majority opinion, you don't have DD. You have what many democracies have now. We'd be electing somebody into power and letting him control us.
Supposing all the representatives of a democracy turned out to be fundamentalist religionists and decided that their consciences decreed that all gay people should be put to death, counter to the expressed majority opinion of their constituents. Mob rule by the minority.
Also, why does the conscience of a person, upon being elected, have more merit than mine.
Maybe the consciences of the rulers of Burma decree that they should ignore/kill the people who oppose them. I'm sure the consciences of South American drug lords tell them that what they do is in the best interests of their families and supporters.

At present I can see no answer. One of the reasons why I joined WDDM, is that here you're actually trying to work out how various DD scenarios will work. The real nitty gritty stuff. Being very busy, I haven't had time to read and consider all the ideas here, so I may have missed some important things that would change my opinion.
Best
Roy