The first point sounds like an implementation issue rather than a protocol one. I also don't agree that most readers have this problem.

Polling rate also has nothing to do with frequency of updates if you care to receive those updates in a timely manner. I haven't seen a reader default to 30 minutes or less.

Probably in both cases you just notice the bad implementations more because they make more requests.

And Atom supports pagination so you can limit the main feed url to be just one entry while still allowing for clients to retrieve older ones.

My only Atom feeds are already short, and the paging mechanism would I think be hard to do in my static site, but yes, thanks for the reminder!