Short answer: no. You will have to meet the requirements for the visa just like every other applicant.Will it affect our chance of being approved the visa, or is the government fairly reasonable when it comes to rural workers.
You say that you've only lived together for 3 months - the de facto visa normally requires 12 months of living together. The only way to get around this 12 month requirement is by registering your relationship (which is possible to do in Queensland) or by getting married. If you are looking to register your relationship, do this ASAP as the longer there goes before applying, the better.
In terms of your evidence - can you get a letter from the boss of the station where you lived to confirm that you lived together there? Do you have contracts to show that you were employed at the same station? Have you transferred any money to each other - have you travelled together and shared the costs?