I used the exact same approach and was unsuccessful using outer joins. Still puzzled why this doesn't work.
I created a report to find all drawings that are not published (have no derived image). Should work with outer join but doesn't. Works by using a criteria of the EPMDoc oid NOT IN Sub-Select Derived Image (the CAD Doc ida2a2 is not in the DERIVEDIMAGE representable reference table).
Seems that there a lot of cases NOT IN as a criteria has to be used instead of outer join.