I can't really remember what was in the novels and what was in the manga, but it wouldn't surprise me if bloodclan was loosely based on the clan structure, and they either didn't fully understand it or didn't care to mimic all of it (or both). because they kind of... entirely missed the point of having a clan? some of the big selling points for the forest clans are that everyone takes care of and protects each other, even the old and sick and injured, and no one has to fend for themselves. but the only teamwork in bloodclan is some of the strongest cats banding together to oppress the weaker cats, and everyone else is probably even worse off than they would be without a clan
so I could easily see them taking the "clan" setup solely for the power structure and nothing else. the cats in charge wanted a formal system that would let them make rules and force everyone else to respect them, and gave it a group name to make it seem more legitimate. whether they didn't know or simply didn't care about the rest, they just had no use for starclan, medicine cats, honor, unity, diplomacy, or any of that warrior code stuff, so didn't bother with it
it would be interesting to know if they knew about medicine cats, though... I agree that they probably wouldn't want anybody wandering around saving weak cats, because that upsets the "survival of the fittest" system, but I would think the boss cats might be interested in anything that could help them personally or help them secure control. unless they were just too arrogant to believe they'd need that kind of help, or too proud to accept it... but if they did embrace it, I could imagine them hoarding that knowledge and dispensing it only to cats they like, to prove that they're truly in control of who gets to live and who doesn't.
it also just occurred to me that they probably don't have access to a lot of herbs in the city... :P