Moodle external RSS feeds are refreshed, if I'm not wrong, by the block visualisation (get_content()) itself. And it causes huge delays when the feeds have to be fetched.
I would change that approach to a global setting to specify cron-timing and to refresh and store contents on cron execution. For sure it'll make it quicker in a lot of courses RSS-intensive not needing "inmediate" refresh.
1) Optionally (default for new installs) move feed fetching to cron, caching results. This can be disabled (????) and it will allow the fetching to work as is now.
2) Store those fetched contents somewhere (i wonder they are now too).
3) Allow to force fetching from the "Manage all my feeds" interface per feed basis.
Not candidate version set for this. Feel free to assign it.