If there is an adverse result as a result of advice given by a doctor, it can be referred to there. It could, I'd imagine, be even taken to court
Yes, I believe it would prima facie form an action in negligence. However, the tort of negligence is incredibly complex and difficult to prove. Most lawyers would prefer another cause of action if possible. In this sense, then, legislation in this area MAY be useful, as it is a lot easier to sue on for breach of statutory duty rather than negligence.
Also, I'm pretty sure there's a statue of limitations on suing in negligence - so after the 6 years (or whatever the time limit is), the patient would have no recourse (in law anyway - not sure about time limits on the Medical Practitioners Board thing).
I do still believe this legislation is a rather ineffective one, but can't really think of any better options.