Mediation is not a dress rehearsal for NCAT. It is an opportunity for the parties to negotiate their own solution, on their own terms. Once they arrive at NCAT they will be subject to the solution imposed upon them by the tribunal.
If the matter is not resolved at mediation that does not mean the mediation has been a waste of time. Parties can learn useful information about the motivation of the other party, how far apart from resolution the parties are, and insights into the likely manner the other party will run their case. You can better understand which aspects matter most to them. This all helps with preparing a strategy for NCAT, or the possibility of reaching a settlement further down the line.