The rocks at Avoca are okay. It's very easy to get to, which I think is partly the reason it gets so crowded. People do get good fish there, but when you're competing for space with 100 other fishermen, it takes a lot of the fun out of it.
Spinning off the rocks there will get you tailor, salmon, kings, & bonito. There are always blokes there fishing heavy gear with livebaits, but I've never seen any tuna hooked. Did see a big cobia there a couple of years back though.
It's a very productive spot for blackfish aswell. You can also catch drummer & groper there.
Fishing the bottome will get you a mixed bag of rubbish fish, but can also get snapper, bream & flatties.
Be patient, and the fish will come, but it's not the sportfishing paradise that some make it out to be.
One last point. Take all your rubbish with you, and pick up a bit of others' rubbish aswell. A lot of inconsiderate people fish this ledge and leave all their rubbish behind. It can get pretty feral at times.
Cheers
Tim