I think from seasons 1-3, the scoobies are still adjusting to all of the fear that comes with the awareness of living on the hellmouth without the same kind of, (if any) control over their fates that Buffy has. Sure, they do a lot to help and in that way are actually quite powerful at times but relative to Buffy, they feel almost helpless; in the backs of their minds they know that if she wasn't around they wouldn't be able to save themselves. The events during the summer leading up to Dead Man's Party really bring this notion to light as they face the forces of evil alone. When Buffy returns, of course, they attack her and call her irresponsible because they spent the summer terrified. Because they also love and appreciate Buffy, the person, they are ultimately more relieved that she is safe and can be their companion once again, so the issue is dropped quite easily.
In season 4, Willow makes quite a lot of progress toward becoming a powerful witch, but she keeps a lot of it to herself. Ultimately though, in this season, the gang continues to look to Buffy to be their protector and they don't question her actions or motives very much which probably makes her feel quite isolated and very much under pressure. Of course this all comes to a head in The Yoko Factor which very nicely sets the stage for their group effort in defeating Adam in Primeval.
After this, things return to how they were before; the scoobies hit the books and express concern but they let Buffy make the big choices.
I think this really takes a turn in Weight of the World when Buffy is out of commission for the first time since the summer after Becoming Pt 2. This time, Willow steps up and takes over, allowing the rest of the gang to put their fear and expectations in her hands. From this point forward, she thinks of herself more and more as almost an equal to Buffy. This is heightened of course when she brings her back to life.
As for Xander, season 5 is the first time we actually hear him acknowledge that perhaps they are putting too much pressure on Buffy, only it happens to be the 'bot the he's talking to when he says "It's ok, you're right, you shouldn't have to know everything." Whenever I hear that I think "finally, someone says it!" It might not seem like much but I think it's a very important step for that to be said, and for the rest of the gang to hear it. This of course precedes Willow's triumphant moment but sets the stage for it.
I think if you look at it carefully, in each season finale in which Buffy defeats a big bad, the scoobies do progressively more and more to help. The more confidence they gain in assisting Buffy directly in averting an apocalypse, the less they lean on her solely for support and the less they are involved in criticizing her personal choices. Of course, the more confidence they gain the more they drift apart from her, and the less they are even aware of the choices she is making and the experiences she is having. Part of this, too, is growing up.
In season 7, all bets are off. Buffy has an inferiority complex about having a superiority complex, and it's a giant mess. Everyone is trying to be a grown up here; everyone is trying to assert his/her independence but is scared more than ever before. If they are judgmental of Buffy's overt leadership, it isn't because she didn't ask for it, like before. She has taken on the role of general now. This is her war and they are her troops. It's a very cold season in a lot of ways. The scoobies are so isolated from one another that they might as well be nothing more than acquaintances, (with the exception of a few key moments), until Chosen. It's sad, but natural I think given all that's happened to each of them. Their life journeys have taken such different paths that the only thing that unites them in this season is the mission, and the house. But the way they come together in the end, with the tie-in to season 1? It's all the more heartwarming because of that.
