A/C Carriers have not been used in high intensity, high threat combat since WWII. They have done a fine job serving as mobile bomber bases against third-world countries with no major air or naval threat and where air superiority is already largely established. A small fleet of shipbourne aircraft could provide a small outer layer air defence (in conjunction with AWDs) and CAIRS capability. I don't believe we need it, however.
We are only facing SU-27/30s in small numbers locally, with larger numbers further afield in Asia. We cannot possibly hope to match the air forces of China and India. Whatever the RAAF ends up with, I think they should focus on the logistical support and manning issues facing defence (perpetually). This is where it all comes crashing down. There is not much point in having 100 JSFs if there are only 70 pilots and only 50 A/C are servicable due to a shotage of maint. staff and spares.