I agree that Cert IV in Financial Services is weak, and being a member of the MFAA or FBAA itself means little, it is simply required by some lenders so many brokers simply join rather than argue the need to join.  Brokers just do it rather than argue and my own view is either body do very little.  FBAA are old hat and probably wont be around in a few years, MFAA are the only competition in terms of an industry professional body and seem to side with lenders more than represent brokers at times.  This might seem like a whinge about them but they in real terms mean nothing when it comes to selecting a broker.  I know good brokers that are members of neither body.
Having owned or currently owning an investment property is a statement used by some to try to cut out those that dont, It doesnt in real terms mean a lot.  A good point I took from a Property Investment author about being educated in every area of property investment rather than purely trusting your 'advisors' is true, might be a heap more work, but is true.  Doesnt mean you dont use advisors but you should understand what decisions they are making (accountants, brokers, planners, developers, project managers, solicitors blah blah)..
Experience does count, but how do you go check up on what someone tells you?
Access to 40 lenders means little, brokers tend to stick to the main ones that are able to assist in a majority of cases, so number of accreditations means little, CBA, ANZ, Homeside, ABL, ING, (in the past RAMS), Suncorp, Macquarie, and Bankwest should cover it outside a couple of mortgage managers most people havent heard of until they need them.
Someone who charges you extra on top of what lenders pay is probably seeking some money in case you dont go through with them, I wonder why they would need to do this?
Basically, you should meet with the broker, and ask them the usual suggested questions which will be easy to answer for most brokers to answer.  It is still an industry with minimal barriers to entry, so you will see hacks, and overnighters come and go.
You can only go with someone who a trusted friend or family members recommends. That is the main point, go on someone who gives you a recommendation, and why they make that recommendation.

And yes you may still get it wrong so good luck.  If you get it wrong however, you can do worse in most other areas of property investment, such as wrong location, bad tenants, just bad luck, bad economic conditions, mistakes with cash flows on a development, etc.  Sorry to send a negative message, I'd rather say that follow trusted friends and family, follow your instinct or vibes and do your homework.