I know someone who has caught a couple of SBT Tuna near Maroubra a few years ago. I have also seen a Marlin close near there. I also know someone who hooked a Marlin on the CC last year. All off the rocks. Put in enough time and something will happen if you have half a clue what you are doing.
A couple of years ago I was on a charter. A guy hooked a sailfish on a shimano btr3500. Best thing was he has mone leader, then mono, then braid, then mono, last mono was lighter than the braid, nearly got spooled, then turned it and landed it. That showed me than anything is possible!!