As of 12/5 the issue seems to be fully resolved. Average response time from Amazon for the BuyShipping API is 3 seconds down from 12 seconds.
Amazon Buy Shipping is currently experiencing excessive delays when fetching rates or printing labels. These delays are on average around 10 seconds.
You can disable Amazon Buy Shipping temporarily and ship your non-Prime orders. "You must use Buy Shipping for at least 99% of Seller Fulfilled Prime products."
These delays may be related to the FedEx-related outages that are ongoing.