It seems to me that priority should be given to closing Questions as Duplicates rather than as "off-topic" qua Problem Statement Questions.

For one thing, a Duplicate is not supposed to be edited for re-opening, while such a thing is explicitly encouraged for so-called "off-topic" Questions lacking enough effort or context.

A [recent instance](https://math.stackexchange.com/q/548889/3111) illustrates the situation.  While a majority of the votes were to close as "off-topic", in fact the real Question is on-topic and has already been answered, so it should never be re-opened.