Just because you have a potential claim under one course of action does not preclude you from following alternative ones. In fact, even if you have successfully claimed workers comp then you can still exercise your right to issue civilly, the quorum of damages will just be mitigated by the monies already obtained. AFAIK, its actually not an uncommon thing for plaintiffs to do workers comp first because its easier and returns smaller and then contemplate whether there is a Tort case worth running; which is harder and more expensive (but you can, if you wish, leverage the workers comp monies into said case).
I think you mean "cause of action" and "quantum of damages" - but you may mean exactly what you typed: if so neither refers to a legal concept.
Its not mitigation - technically money paid is a defence but only if its paid by the person you seek damages from (mitigation is something a plaintiff is obliged to do - i.e. there is an obligation on the party claiming damages to take all reasonable steps to minimise the damage they suffer).
As for leveraging your comp payments the fact is that there are plenty of firms who act on a no win no pay basis and who fund the disbursements necessary to present a person's/company's "common law" or even Trade Practices case. Comp payments would fund about 1 hour of a single lawyer's work per week, if that, so it would need to be some kind of massive lever to get you anywhere.
The reason people get their compensation first is that workers compensation does not require proof of fault in the employer for it to be payable and so, in the case of a frank injury, entitlement is easily established whereas proof of fault, even in this imaginary and illusory case, would involve retention of a number of experts by all sides before it could be tried.
The certainty with which some of the propositions have been advanced in this thread causes me to wonder how accurate any of the rugby views expressed elsewhere on the site are likely to be.
