The excise on beer is more complicated than for wine, and...

The excise on beer is more complicated than for wine, and doesn't make sense.
The recent change is good, but still doesn't fix the issues that small breweries face.

Wineries pay a flat 30% tax on the value of the sale of the wine at the time of the sale.
Brewers currently have 6 tax rates based on the container size and the percentage alcohol.
The first 1.15% of alcohol is not taxed, but the rate goes up for mid strength and full strength beers.

The container size threshold (ie 49 litres) was designed to protect pubs, by encouraging the consumption of tap beer, rather then bottled/canned beer.
Because most of the pubs are contracted to one of the two big breweries, it makes it very difficult for a small brewer to get their beer on tap.
The alternative is to put their beer in bottles, at a 50% higher tax rate, in addition to the extra cost of bottling, labelling, packaging etc.
Brewers also have to pay the excise up front, at the time of production, which could be several weeks/months before the beer is eventually sold.

Wineries get the first $1.5M sales tax free (via a $500K excise rebate) regardless of how much they produce, ie the big boys get this rebate as well.
Breweries used to only be able to get a 60% rebate of their excise paid IF they produced under 30,000 litres per year (ie sales of approx. $120,000 @$4/litre for wholesale keg beer). Even the smallest commercial breweries produce more than this, and a lot of them are not viable.

In the US, the excise rate is about $1/100 litres compared with $1/litre in Australia.