For me, two major things always get in the way of judging Joyce, every time I want to.
The first is the gigantic pile of extraordinary circumstances she's faced with, having a daughter as a slayer. I mean, I understand the metaphor here and of course parenting is always unbelievably difficult. But take the events of Becoming Pt 2 (as others have pointed out) alone during which she finds out Buffy's a slayer in cahoots with a vampire and is about to kill her ex who is also a vampire in the span of like an hour--and the whole thing seems almost silly to me. I mean I kind of chuckle to myself when I imagine how any parent is "supposed" to react to that information. Whether or not it's merely a hyperbolic telling of what having a teenager is really like, the cold hard fact for me is that the circumstances are too extreme for me to know how to react.
The biggest however is that I think Joyce is purposefully kept "quiet" or "on standby" by the writers for the purpose of moving along the plot. In essence, I see a lot of her reactions-- which I'd be quick to judge as negligent in other circumstances-- as plot devices, really. I hate talking like this about the show; throwing it so harshly into reality by talking about the writing techniques used, but honestly, I really can't look at Joyce without thinking about them. I mean, considering the woman wasn't passed out all the time--that she wasn't an alcoholic, a drug addict, or just plain negligent to the extent that child services should be called, she really would have noticed the blood and/or the grass stains at some point. She really would have noticed that her daughter went out at night, eventually. I mean, it was just the two of them living in the house and assuming Joyce ever called out to Buffy past 8 pm and never received an answer, she would have walked into her room and noticed she was gone. Parents who are remotely involved in their child's lives are at least capable of noticing such glaringly obvious things. Even if she was a not so fantastic parent, this would be the case.
When Dawn cut her arms open with a knife, did Joyce insist that they go to the hospital to confirm that the wounds weren't deep enough to need stitches? Either she isn't too concerned with the well-being of Dawn which is not consistent with what we know about Joyce, or it has to do with the inconvenience of writing that into the script.
--If Joyce acts too often as a figure who says "no" or is suspicious of the gang's operations, the plot doesn't move forward. They are all doing terribly risky things every minute of every day so conveniently, the authority figure needs to be someone who encourages them to do so with a guiding hand, (Giles). If Joyce starts acting overly concerned or encouraging the gang to be safe, we won't have our show.
So anyway, I can't really judge.
