Am I saying they should promote hard drugs?
They shouldn't promote them, just sell them from a trusted specialized shop instead of a street dealer who's main goal is to get you hooked and earn more.
I personally don't know what the recommended heroin dose is, but that's because I'm not an opioid expert.
For MDMA, the recommended amount is 1 ~ 1.5x your weight (kg) in mg (e.g. 80kg, means 80~120mg) for women and 1.5 ~ 2x your weight in mg for men (e.g. 80kg, means 120~160mg)
When using once every three months, your brain damage will have recovered and so will your tolerance, therefore, you can use this same dose again.
Otherwise, you'll have to build up and feel what's right for you and accept that damage is building up.
Like I said, abusers will be there, whether it's legal or not.