Yeah, I'd say it's a blessing in disguise that the dope you've done isn't getting you off the way you were hoping.
It could any number of things really. Maybe heroin just isn't your kind of high; it happens. Maybe snorting just doesn't do it for ya. Again, a blessing in disguise because if the needle does do it for you then watch out!
It could be lousy dope. If I did 2 of baltimore's raw with your tolerance, I'd get in a car wreck (in fact I did total a car after 2 of baltimore's finest and that was with a tolerance). However the dope I get here in New England, with no tolerance I usually need 2 bags IV to feel reaaaaaaaal good and that wouldn't even cause a car wreck. And currently I do have a tolerance. (Note: I shouldn't have to say this, don't do drugs and drive. I was lucky that it wasn't worse and I don't do stupid stuff like that anymore)
Maybe the dope your getting is the bottom of the stash so it's a little faded and not as potent.
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Maybe it's an acquired taste for you.
Maybe you've overhyped it and it's not living up to some sort of magic drug wonder status to you. I remember feeling this way about coke. Though when I IVed coke the first time I was like "oh! now THIS is what coke is about! Hey what do I have lying around that I can sell because I'm going to need more of this ASAP!" haha.
My personal feeling, be glad heroin isn't everything you wanted it to be, because for too many people, it is and it becomes a life long struggle.