I'll admit I haven't done much research on opiates specifically for the simple reason that I have never known any active opiate addicts (though, I did get trained to administer Narcan). However, in my understanding of drugs such as coke, MDMA, or speed/adderall, which are more common in the tech scene, higher purity is unambiguously a net positive. It's been a while since I was actually involved in the overlap of the tech/festival scene but when I was around that more, I made anyone I knew used drugs aware that I had drug test kits and would let you borrow them no questions asked. I can't claim I ever saved a life, but I can say for certain that ~30 people at a festival I went to ended up riding out bad trips in medical tents or being transported to the hospital due to MDMA cut with DOC, and none of the people I let borrow my test kits at that festival did.
If you look at who generally dies from drug overdoses it's largely opiate-based drug users. I once listened to two junkies who hadn't seen each other for quite a while talking and letting each other know about who died. They were mostly talking about overdoses, the conversation went on for about 30 minutes non-stop with different names non-stop. None of the cokeheads, eckyheads (MDMA), or speed freaks I knew ever had conversations like that.