Here, too, the changes I would make are minor and mostly have to do with wording.

“Magnificent afflict” is definitely not the phrase you want to use here.  “One of the most important difficulties” would be better. 

The word “had” in that sentence should be removed.

“Discrimination” and “mistreatment” typically do not get made into plurals.

Do you need to define “blackbirding” or is that a term that has been introduced in your class and/or is in common usage in Australia?  Here in the US, it is not a commonly used term.

In the sentence that begins “They signed…” the word “discriminates” should be in the past tense to agree with the words “signed” and “revealed.”

In the last sentence, you should start with “The Australian Government…”

Finally, please be sure to cite your sources in the finished document.  All of these statistics need to be cited.