Agree, having worked extremely closely with Police, Ambo's and even firey's here in my job, they all say the same as your experience, Meth is one hit and your hooked. The danger they become too all around means legalising it would be asking for trouble. As you stated the issue even with Cannabis is the drug syndicates now lace it with meth to get the full addiction so they come back for more. Legalising dope may mean a cleaner dose as you mentioned when manufactured through regulated organisations, but will it stop the progression to the illegal laced doses? Most addicts start at alcohol, then try dope and just keep looking for the bigger high trying new drugs to get a bigger high again. I agree that is not all, but even dope is to a large extent a gateway drug in my view and that is a risk of it being legalised.
The Meth hook is also why the scum bag dealers hang around footy clubs especially in regional areas, give them a free hit and have a customer for life!