I didn't know it was this good to be honest. Thanks for working it out!
I actually think that anything in or around the 10K mark is pretty good for the A-League considering what football is generally up against in terms of other sport in Australia.
If you're really trying to find a negative then it's probably the perception that grounds can quite often look sparse in terms of the crowd. Brisbane being the prime example. If you're playing in a large capacity stadium and it's less than a quarter full then it's always going to be a bad feel.
It's like the time I once saw Queens Park FC in Glasgow playing a mate's team Falkirk at Hampden Park, which was Queens Park official home ground. There was 4,000 in a 50,000 stadium and it wasn't great. Massive game for Falkirk's 2,000 fans playing at the National Stadium in Glasgow but no atmosphere. When I went to a game at Brockville, Falkirk's old ground there was 5,000 fans in a 8,000 capacity stadium and it felt lively as!!!
Perception is the key to A-League attendances.