Alternatives to using subqueries as parameters?

Question

I have a very large non-partitioned table that is taking a long time to return results from this query:

SELECT 
    (SELECT Listagg(VALUE_STRING, ', ') 
            WITHIN GROUP (ORDER BY VALUE_STRING) AS VALUE_STRING 
     FROM   ATTRIBUTE_DATA AD 
     WHERE  AD.id = DT.dataid 
            AND AD.defid = 3070056 
            AND AD.attrid = 4 
            AND vernum = (SELECT Max(vernum) 
                        FROM   ATTRIBUTE_DATA AD
                        WHERE  AD.id = DT.dataid 
                                AND AD.defid = 3070056 
                                AND AD.attrid = 4) 
            AND defvern = (SELECT Max(defvern) 
                        FROM   ATTRIBUTE_DATA AD
                        WHERE  AD.id = DT.dataid 
                                AND AD.defid = 3070056 
                                AND AD.attrid = 4) 
    GROUP  BY AD.id) AS PlantNumbers
FROM WORKTABLE W 
    left outer join CUSTOM_FORMS FORMS 
                ON FORMS.volumeid = w.subwork_subworkid 
                    AND FORMS.versionnum = -1 
                    AND FORMS.rowseqnum = 1 
    left outer join DATATREE DT
                ON DT.name = FORMS.document_number_text_field 
                    AND DT.ownerid = -2000 
                    AND DT.SUBTYPE = 144 
                    AND DT.dataid NOT IN (SELECT dataid 
                                        FROM   dtreeancestors 
                                        WHERE  ancestorid = 3109628) 

When I take just this subquery alone it takes 12 minutes to run:

SELECT Max(vernum) 
FROM   ATTRIBUTE_DATA AD
WHERE  AD.id = DT.dataid 
   AND AD.defid = 3070056 
   AND AD.attrid = 4

How can I improve this script.