I think it probably has something to do with the way the quotes are often blended into your writing. My brain reads a single sentence or paragraph and doesn't distinguish which parts were in italics, so it seems like there's more badfic than there actually is.
As for sketching in, it's a couple of things. One, it seems like you let the badfic do a lot of the description for you, especially when it comes to the setting. Or maybe there just isn't much description, period. Meaning, I know the setting is Grimmauld Place, and sometimes there are curtains, and sometimes there's a table or a bed, and if the fic goes to a corridor there's a corridor, but that's about it. ... Which sounds dumb when I write it out, because it's not like I expect elaborate detail about everyday objects like a table. It's a table, it's got four legs and a top, there are chair legs and feet around the sides. But, when the agents are hiding behind the drapes, for instance, they spend some time there, and it might be good to know more about them. Are they black drapes? Are they heavy and ornate, or thin and filmy? Are there holes in them? Do they smell of mildew, mothballs, dust, something else? How well can the agents actually see out, or at all, for that matter? Is there a window behind them, or just the wall that Library smacks the Doxy into?
Two, there are long stretches of "couple lines of badfic - couple lines of agents reacting - line of badfic - line of agents reacting," etc. Most of what we get about the agents in those stretches is dialogue. There ARE points where you describe how they're positioned relative to each other and the setting, and interacting with each, which is good, but in general I had trouble connecting with them as physical beings in a physical environment. Which goes back to point one, I guess.
Also, we don't really get inside their heads much. Taking the drapes sequence as an example again, I know Library is annoyed and possibly in pain when the Doxy bites her because I see her teeth grinding and her eye twitching, but I guess I'd like to know more about what she's thinking in that moment. Also, I don't remember the effects of a Doxy bite and I'm assuming people who aren't Iximaz might not, either, so filling in the pain and whatever other effects she's experiencing would be a good way to flesh out that passage more. You don't say where she was bitten, either, which leaves a big blank spot in my mental image of the story.
Another thing missing from early in the mission is their disguises. JF complains that they're not students, and Library comments that the students wear Muggle clothes during the holidays, but you don't say how they're actually disguised. Did they use disguises at all, even?
So, all in all, there's not too much badfic, really—just not enough of what I'd like to know about the agents and what's happening to them.
Formatting errors:
1. "You can stop sounding off, we’ll go on the mission as soon as she’s clean and dressed. ”
2. Missing line break between the paragraphs beginning "I don‘t know why we couldn‘t be disguised as students" and "This ‘story’ doesn‘t take place anywhere near Hogwarts." There's also three backwards single-quotes in there. (This is why I don't use so-called smart quotes.)
3. Speaking of which: "considering the 'artist''s attention span"
4. Missing line break between “Yes.” and “Also the half-vampire isn’t stupid because she’s an American, but because she’s a half-vampire so can I charge for that too?” (Also, you want commas around "so can I charge for that".)
5. This may not actually be in error, but I noticed that some badfic passages only have single line-breaks between paragraphs?
6. Hyphens where there should be em dashes throughout. (You can teach Gdocs how to make em dashes from double hyphens by adding to its autocorrect, FYI.)
7. The following passages have extra first-line indentation:
“Yeah, I cou- hey, wait!”
The older agent suppressed a smile.
...
“Uh, I can cook a mean one?”
Library sighed. “Stakes, not steak.”
“Ohhh. ...Can I use fire instead?”
“I suppose.”
...
Snape asked her to at least try, [etc.]
He accepted, and the two left. [etc.]
...
Patience and her also uncanonical mother had a dramatic scene [etc.]
...
Library sighed, kicked out her leg, and was soon rewarded with an ‘Ow!’ when her heel met JF’s shoulder. “Stay there.”
“But but but but Snape just used a judo throw on her! And I wanna kill her!”
...
The entire post-mission sequence after the horizontal rule except these lines:
“Stay here and don’t set anything on fire.” She wasn’t entirely sure that JF would be able to manage even that, though.
“Fine,” and with that, JF immediately slouched into a chair.
... I think that's it.
I hope that's all helpful and not just upsetting. I do agree with the good things other people have said, btw, and above and beyond anything else, it's really nice to have you back in action. {= )
~Neshomeh