I would prefer it if they skipped out on some of that, yeah. I skipped over it myself, in watching the subs. It just wasn't worth my time.
I mean, I don't want to watch a person's backstory five times in the course of a show, unless each time it reveals something new. And I mean jeez. I had JUST WATCHED Robin's in full, and they repeated it?! They must really have been desperate to stay behind the manga. I simply read the descriptions on Wikipedia (<3), and decided not to watch useless episodes.
The Chopper Rumble ball incident… I'm not sure. I guess it could go either way, but I'd say keep it in for continuity's sake.
This is not to say that the dub needs to skip all fillers. NOT AT ALL. There are many fillers I really truly enjoyed watching (G8, for example). But those flashbacks were placed at a time in the anime which to me made them very annoying. But that's just my personal opinion. In the end, it's FUNimation's decision. I will still refuse to watch those episodes, however, and avoid buying those episodes at all costs (If they're on the same disc as IMPORTANT episodes, my hand will be forced, and I'll be none too pleased, but I'll buy it)
As to Crazy Rainbow & etc.,
You could always put the song, and thus the credits, at the end. skip to the recap of the Gol D. Roger speech in the beginning, where the song is.