I'm not sure if this will help as I've already migrated to 7.5. We were running 7.1 SP1 at one point and I remember having this exact same issue. I've looked through my old SQL queries from those days and found these two:
-- Find tickets not closed without tasks
select process_id as 'Incident ID'
from ServiceDeskIncidentManagement as im
inner join ReportProcess as rp on rp.ReportProcessID = im.process_id
where not exists (select * from task where WFTaskNumberPrefix = im.process_id) and (rp.Result <> 'Closed')
-- Find tickets with tasks and no assignment
select WFTaskNumberPrefix as "Process ID" from task as t
where t.iscompleted = 0 and not exists (select * from taskassignment as ta where t.taskid = ta.taskid)
I think the bottom one will help in this scenario and you should be able to add this to a report.
Hope this helps!