Depends on the number of applicants into the course. It's important to recognise that clearly in ATARs (as published on uni websites) are only indicative and change each year (not by much, but some do). Given you've got SEAS from underrepresented school + your personal circumstances, I would say it could be possible still to get in.
However - make sure you keep this in your first preference if this is what you definitely want to do! Don't worry about the ATAR requirement - you could still get in. I would also think of a few alternatives / have a backup plan B too... just incase!
If you get a lower offer (e.g. 2nd preference or lower), you are able to rearrange your preferences between each round (each round operates the same - you order your preferences and each round your application is considered). If you don't get the course you want - accept the offer you get in the first round anyway, you will be able to withdraw from it if you happen to get that RMIT course in 2nd round. Good luck