Writers for BtVS and AtS were able to experiment more with the dialogue because the words themselves are only part of the Voice on a TV show. The other part is consistently supplied by the actor who's always going to look like the character and always sound like the character, bless them.
But when it comes to writing the characters without the actors' voices, you've got to be on the money. Especially when the piece is purporting to be the canon continuation of BtVS. And it hurts to say that Season 8's #24 Safe just failed this test because I like to be unfailingly optimistic about Season 8. But it's been a long, hard fall from No Future For You's Faith and Giles dialogue by the talented Brian K. Vaughan. If Vaughan gets an A in Whedon dialogue with a major in Faith and Giles, then Krueger flunked out.
Ok, maybe that's a little harsh. But yeah, I think the metaphor stands. The closest Krueger got to playing with the language was having Faith say "Octobitch". And it still felt awkward. Faith's dialouge lacked that swagger that she always imparts. Giles dialogue lacked wisdom or a baseline normal IQ.
In the Whedonverse, language isn't necessarily the most important thing. Witness Hush. But if you're not writing a creepy and funny story where your characters actually can't speak, then you need to be nailing that dialogue. If you're not comfortable writing some wordplay, then please allow me to show you the door. Thanks for visiting the Whedonverse, but I'll be even more thankful the nonplayfuls aren't staying.