Here is the thing, some highs are much more potent and addictive than others. Growing up in the 90's and having seen the damages of heroin, I'd say no, it doesn't matter whether Tobacco or Alcohol are also legal.
Legalizing drugs would make drug addicts far more accessible to drug treatment schemes. Regulating the supply would additionally make being a drug addict a lot safer and less dominating for one's life. Heroin is safe. It's the universe of things around heroin that kill. Lots of being murdered, and going to prison; fent ods, MRSA infections, liver failure from Hep C, AIDS; doing crime and betraying everyone you know to get a substance that costs a nickel a dose to manufacture. All of these are symptoms of drug enforcement, not heroin.
Legalized and taxed drugs make them safer for all and reduce the amount of deaths we see from overdoses.