Its not a black mark on your CV, companies have the right to employ or not employ a 457 holders/spouses. Both my husband and I have been a spouse on each others 457 and both of us got full time permanent employment being a spouse on the other ones 457, redundancy happens to anyone. I am now a spouse holder again on his 2nd 457 and am in a full time permanent role (not contract) and am treated like any other employee. My company have offered me a 457 too so we can both be on them separate to each other so we have fall back if the other were to face the redundancy fate again. As for our roles, they are not run of the mill and too are very niche but are only on the CSOL list so 457 was our only option.
Also as for research, you are moving to the other side of the world! As stated by everyone in this thread you do as much as you can e.g professional migrant agents, friends/relatives if applicable, emigration shows, call companies and recruitment agencies in Oz before you make your mind up to see what the market is like for your spouse, get networking before you go. Research your own job, is there a market for it here or is it so niche that it is limited to one or two organisations including the one you came out with.
To take the advice of one source before you make a massive leap like moving to the other side of the globe is ludicrous! You should have weighed up the pros and cons of leaving your job in the UK and made sure you were coming with ALL the facts not just those of your new employer who seems to have got you out here, used you for what they needed and now you are surplus to requirements.
The 457 is a great Visa but is a risky one too so coming from someone who has the t-shirt and is still wearing it after 2 redundancies I would tell anyone to go for it but only after some hard grafting research to see if it is right for them!