I'm not sure what the tax is in Australia but in China it's zero....the salary is after tax and the employer pays the tax for you.
Also, at most Chinese carriers you get far more than 42 days paid leave per year. I think most contracts are a minimum of 90 days with up to six months paid annual paid leave for a bit less salary. On top of that you get the scheduled rest days to comply with regulations and flying limits.
Last year I flew about 550 hours and had about 130 days paid leave outside China. I also took a bunch of paid sick time.
Chinese contracts aren't paid on an hourly rate. You are guaranteed a salary with overtime promised after 80 hours. Some pilots pile on the OT, some don't. There are almost always other paid benefits such as annual guaranteed bonus, housing allowances and travel allowances on top of salary that amount to a few thousand more per month.
Yes there are disadvantages to working in China but there's also many advantages. For the most part I wouldn't recommend it to any but young and single people who don't have significant attachments to family or who's family will come with them. I also recommend trying to be based in a southern city with less pollution and a better climate.
As far as job security, I think it's no different. Pilot jobs are never stable anywhere but I've never heard of a Chinese carrier furloughing foreign pilots before.
If you have a decent paying and relatively stable position elsewhere, keep it.
Mostly I would just like to set some facts straight.