1/1000 people who use meph dying is innaccurate. As far as I know, either none or only a few people have died from mephedrone alone. A few people have died from combining it with other drugs.
The relative dangers of a drug aren't good logical grounds for making it illegal. This is because, no matter what you do, people will continue to do drugs. By legalizing drugs you ensure several things- 1. Drug gangs don't exist. 2. Drug use contributes to the economy. 3. Those people who choose to get high can aquire clean, safe (in terms of cuts etc) drugs and means to use them. 4. The prisons aren't filled with people who did nothing but make a personal choice.
People should be allowed to do what they want to themselves. If you want to smoke meth, I think you should be able to aquire clean meth and the supplies to use it as safely as possible without the risk of prison. I think education and health services should be provided. If you want to do drugs that are harmful, then at least you could do them as safely as possible if they were legal.
Whether a drug is harmful or not has nothing to do with whether it should be legal or not. They should require the makers of these bath salts and incense and fertilizer and what not to include a list of ingredients. That's not going to happen though, because it would require them to allow these products to be sold for human consumption.