It's easier, cheaper and therefore better to let ASIC do the...

It's easier, cheaper and therefore better to let ASIC do the prosecuting in the first instance, as they have much greater investigative authority and funding than any of us do. Then when they are successful come in with a Class Action for damages, probably on a fee for success basis.
[I think - not legal advice].
P.S. the weak point here is the offending ASX member broker, not necessarily the actual party giving the instructions, who may well be nominally based in some difficult to prosecute jurisdiction such as the Cayman Islands. The Australian based broker can't easily escape ASIC's grasp. Unfortunately they can escape Civil damages by liquidating.
I'm guessing if the ASX has been found truly negligent in not enforcing their own Regulations, then they could be successfully sued for damages and could theoretically be legally squashed like that big fat slug in the proverbial vegetable garden. A locally based target, too big to escape.