S.24 of the Transport Safety Investigation Act (2003)
On a quick reading of the legislation, I doubt that the action of the aircrew departing for Dubai would in itself be construed as hindering the investigation under s. 24. It would of course be expected they would be avalable for interview when required by ATSB. Of course there is a requirement to file an accident report, and to allow access to the aircraft and flight data. No doubt this will be done by the company on the ground in Melbourne. There may also be obligations under the treaty. BTW I am a senior Australian lawyer but with no particular expertise in aviation law.