Katerina, I love your style. You have such a great eye for drama in an outfit, without going too over-the-top. Yes, you have a "formula" of sorts, which is great because it means you really know yourself and what you like. I feel like it doesn't matter what I think about whether some of your black jackets duplicate the functions of others; what matters is that, for YOU, they have different purposes.
I have many many tank tops, because high summer is my prevailing season. Does one navy blue tank top duplicate the function of another navy blue tank top? Absolutely. However, one navy blue tank top is very edgy in its design, and another is more plain or minimalist in design. My problem is that I actually have over half a dozen navy blue tank tops (I'm very afraid to actually count them LOL); yet, in my mind they all have slightly different moods that they "go" with.
I figure that if we have room for all of our black jackets and navy blue tank tops, then its perfectly okay if they duplicate the function of the others. Fashion is a very easy way to communicate about ourselves, and each black jacket or navy blue tank top says something different.