Rob, thank you for your reply
what are the limited exceptions?
The appeal is over the original case
the action in the court below had two parties, but more than two persons involved
The original action was adjudicated although there was no cause of action (believe it or not!) [defence was filed, sealed and served without compulsory evidence-on-discovery, or valid pleadings for that matter] (yes, I know what you are thinking..."I'm talking to a lay person who is evidently on a high dose of illicit drug", but what I'm saying is never the less true; to add, I found that legally speaking the expert witness was mentally incompetent, and it wasn't her first time in court in that capacity)
The responsibility for this is born by the Registry of the court below (waving-through defence filings, and later the amended, and further amended defence and cross-claims), the justices (both retired) who failed to identify Registry errors, the justices who applied a wrong precedent (yes, you will again say "he is nuts" but NO ONE involved had read the cited authority!), and the legal practitioners who failed to inform the Court about these errors of law (and there are others, never mind errors of fact, e.g. justice not reading a medical report on sustained injuries but questioning why the person typed instead of hand-written a document)
Suing the Registry would be a new action v R, and justices are immune from prosecution, so...
In regards to parties, r 50.5 UCPR (NSW) refers to person
(1) Each person who is directly affected by the relief sought in the appeal or is interested
in maintaining the decision under appeal must be joined as a defendant.
Since all legal representatives would be either directly affected by the relief sought, or interested in maintaining the decision under appeal (admitted in Court), it seems to me they are all necessary parties by definition of r 51.4 (which repeats 50.4(1))
(1) Each person who—
(a) is directly affected by the relief sought, or
(b) is interested in maintaining the decision of the court below,
must be joined as a respondent.
the r 51.4 (3) The Court may order the addition or removal of any party. - seems contradictory to the "must" in (1)
Since the "may" in (3) is discretionary, it does not override a duty of a "must"