Assuming that across the board 50% of people are refused the first time due to administrative error on their own part, then maybe one way is to make the visa application process more easy to understand. Perhaps some kind of information could be more available to people who are applying, which hopefully would reduce the error rate.
But still, even if 50% is the figure, we need to look at the other 50%. Having some kind of a review mechanism I think is key. Even if you want to do it as a pilot, as Victor has suggested, we have to look at why these visas are being refused. As you said, if it's a policy issue, then why is it we have a policy that allows dual intention and we still see some of the applications being refused based on that?
Maybe a review system, not by the actual visa officer who made the decision but by another officer or department, or another mechanism, could look at the decisions and the reasons for refusal as well so that we know that the policies are being consistently applied.