I’m experiencing a similar issue. In my own case, a new installation of WP has worked fine for a few weeks, until it suddenly took 90 seconds to log in. Removing the calls to fetch_rss has reduced the login time to a few seconds, as above.
I’ve timed an individual call to fetch_rss at 30 seconds exactly, which suggests that something somewhere is failing, then timing out. But my experience with this is to limited to progress it much further, at least at the moment.
Please someone! Any help?