Birth, marriage and death records belong to the states, so they would not be in the national archives - each state has its own archives. Others have already answered for how to look up Victorian deaths online where possible.
I don't know what date range might be covered by http://tributes.theage.com.au/
for newspaper notices in a major Victorian newspaper.
Someone else mentioned Trove, but did not explain it. https://trove.nla.gov.au/
is the National Library of Australia's website with a lot of old newspapers. Most of them are online only up to 1954 for a mix of copyright and cost reasons. The text is machine OCRed, but the website encourages crowd-source fixing of errors so the text gradually improves.