Not at all, IMO. I could quibble on this and that, but overall I saw the "Dark Willow" arc as the "Wiccan (*) equivalent" to Faith's own dark journey, and that her corruption was more of hubris (as Faith experienced) rather than addiction.
And let me add that as someone raised for the most part by 2 wildly dysfunctional alcoholics, and someone who has been around addicts, including the homeless kind, about the closest you'll get to the Reefer Madness nonsense in the real world, that the "magic addiction" arc came off as painfully stereotypical to me that just didn't resonate with my own experiences with addicts, including with an old homeless (and wanted by the law) heroin addict at rock bottom that I'd formed a close bond to in my youth. Let me also add that I've never been an addict, and never even experimented with hard drugs like heroin, so I was on the outside looking in, just as I was as a viewer of season 6 Buffy.
(* As should be obvious, I mean "Wicca" in the Buffyverse than the real world, though I know at least a few Wiccans seem to try to learn Wicca from the show...pretty cringe-worthy stuff, though I was intrigued by an experiment one was thinking of doing, one that essentially drew upon a character like others would draw upon a god, but as I think they're all Archetypes anyway, I thought it might work.)