Please be gentle, I'm a first home buyer!
1) In your experience, what do mortgage brokers do that online comparison tools can't?
2) Did they try to save you money, or did they try to drive you towards a mortgage that pays them the best commission?
3) Right now, with a 30% deposit, for Live-in variable with offset account, I'm getting a touch under 5.1% on Rate City. Is it worth going through a broker, or am I better going it alone?
1) They have a wider range of options open to them and can better assess your case and suitability to certain offerings by tweaking the "right settings" from their knowledge base. They can also negotiate with counterparts in banks/lending institutions for slightly better rates and added bonus features like cashback. They also clearly explain to you what offset account vs redraw account means in real world terms.
2) Both. They have a really good incentive to save you money so you sign-up with them and they can then get their commissions. Otherwise you would simply go elsewhere and they lose out completely.
3) It's always worth having a chat with them and see what they can offer. You lose nothing. Try this guy: https://www.blueowlfinance.com.au/book-online