Just too many characters to develop perhaps?
That makes sense. Most character development seems to be about only a handful of rabbits; the odds are that nothing much was lost by excluding Acorn, Buckthorn and Speedwell from the film and TV series.
5 days of
=>
= 
(It does seem like fun to torment Hazel a bit... I wonder what Fiver thought of it all?)
He might have been just as annoyed as his brother. Or perhaps he just stayed in a corner of the burrow meditating on his visions, ignoring Hawkbit entirely.
I really should write that fanfic
Chapter 5. It's a rather slow chapter. Several paragraphs are spent describing the area where the rabbits are, and how afraid and tired they are; this is well-written.
We do get a bit of character development for Dandelion, how he is the fastest of the group and an expert storyteller.
We also learn some more about Dandelion- he's very fast (in contrast to his series' counterpart- I believe in season 3 there was instance Dandelion couldn't keep up?)
I just took a look; yes there is, in The Betrayal. Spartina is leading everyone to Darkhaven. Hazel and Bigwig are ahead, followed by Hawkbit, and finally Dandelion and Fiver, far behind.

We're slow, but steady...
*both rabbits collapse on a fallen tree trunk*

No, I think we're just slow...
Also, during the dog run in The Invasion, the dog almost kills him and Fiver has to save him...
I really prefer book Dandelion.
As for the first mention of El-ahrairah...I had forgotten about it, I thought that the blessing story was the first introduction to him. What I find the most interesting about this is the fact that he can control the weather. I don't remember this happening in any other stories, either in this book or in TFWD.
I don't really understand the comparison with John Henry either...
One last thing:
the extraordinary, rank animal smell that seemed to come from somewhere rather nearer [than owls]
I have a feeling this might be the lendri who shows up at the beginning of chapter 7.