It is not exactly a myth.. I have had a few friends overdose on this exact combination, by using too much of one or the other... and they had a heart attack and died.. it was horrible.. but I once almost died myself, mixing not heroin, but oxy with crack, along with another CNS depressant which was klonopin, and that makes things much more dangerous.. opioids of any kind(mainly strong ones), mixed with coke/crack and benzos.. I was smoking crack and had sniffed about 150-200mg of oxy while also smoking another at least 100mg of oxy too, along with and between crack hits... and I had taken about 4-5mg of klonopin throughout that day and night... well I got extremely lucky because I almost died for sure, I blacked out once after way too much of both drugs were being smoked the oxy on foil chasing the dragon, and the very strong crack I was smoking... I took a hit of oxy, after about a G of crack or more, had been consumed at that point, and just blacked out, fell down and hit my head on my dresser... woke up feeling very strange, like I had no idea what just happened, say the giant bruise on my head and my lips took on a purpleish coloration and skin became very pale.. I was scared, but also very high, so being the addict I was, continued to smoke the crack and oxy... and well this time, I got VERY lucky.. I had invited a very good friend of mine over, and he was a good enough friend, and the only one who knew where my hidden house key was outside, well when I took either another hit of crack or oxy, I believe it was a hit of crack this time, I again fell down and collapsed... was out for a good minute, and I awoke from complete darkness and not having a clue, again what was going on, in my cold shower, with my friend giving me CPR... and I just popped up like WTF! what are you doing motherfucker! I was pissed at first! lol.. I told him to get the fuck off of me, not having any idea I had literally just died for about 30 secs- a minute and miraculously my friend had let himself in when I was passed out, not answering my phone or door... he saved my life, and after I found out what had happened, I thanked him! very much! so I never did that combo again after that... I did stupidly mix coke/crack with opioids, but didn't mix them both with a benzo after that.. if so it wasn't much, just like 1mg or less of any given benzo, usually kpin or Xanax at that time... So yes.. its not a myth, and you can totally get away with doing that, most of the time, ONLY IF you don't do too much of either one... or aren't totally opiate naïve or whatever... be safe! and don't let yourself to too much!