Depends. Are you looking for (in any combination): (a) compensation in the form of monetary damages/coverage of costs, (b) to bankrupt the person, (c) to stop the damaging conduct, (d) an apology?
(a) - You're going to be out of luck.
(b) - You're going to be out of pocket on a mean spirited principle which will likely have zero practical effect.
(c) - If successful, you should be going for an injunctive order to requiring the person to stop their defaming conduct. Of course, they may not follow that anyway - but at least you'll have an order you can use and produce to third parties.
(d) - If successful, you should get this as well (in writing). It will likely be through gritted teeth but, again, you'll have it to be able to use it and produce it to third parties.
HiIs it worth going for a defamation lawsuit if I am aware that the defendant has no assets and only recieved a carers pension from centerlink?