Does DIBP owe priority 5 applicants a moral obligation to process their applications?

DIBPs priority processing arrangements generally categorise skilled migration applications into 5 groups giving regional employer sponsored visas the highest processing priority. While the top groups can have the visas processed within months, those in group 5 can wait well over 5 years without any indication of a time-frame as to when their applications may be processed.
It almost looks like after accepting valid applications and the visa charges, DIBP has just about simply forgotten about processing the applications categorised in group 5. Is DIBP hoping that if they make these applicants wait long enough the applicants will simply give up and go away allowing DIBP to pocket the application fee for doing nothing?
Legislation allows the Minister several mechanisms to ensure visa grants are managed in line with the annual planning level. These mechanisms can either restrict or increase the level of visa grants. This excuse is often cited when the issue is queried. A recent response on the issue from DIBP stated outright, “The Department is unable to give specific timeframes for when individual applications will be finalised,…” [http://migrationalliance.com.au/immigration-daily-news/entry/2014-09-priority-group-5-applications-for-886-and-176-visas-dibp-update.html]
Upon receipt of a valid application, DIBP surely must have an obligation to process an application within a reasonable time-frame or inform the applicants of the likely time-frame. In the alternative, DIBP should at least allow applicants who wish to withdraw their applications to do so with a full refund. Perhaps this may help speed things up for those who choose to wait.
Some estimates (unverified) state that there are over 40,000 applicants in the priority 5 group, with some applicants still waiting after 5 years with no indication of when their applications will be processed.
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