@Neutralizer, I believe you have it backwards here, at least if you’re talking about a user’s experience visiting your site: OCSP stapling means that the OCSP response data is sent by your server along with the certificate, so that a visitor’s browser doesn’t have to query the Let’s Encrypt OCSP servers to check that your certificate is still valid. In this regard, OCSP stapling should make your site’s availability better, not worse, in case of a Let’s Encrypt outage.
Unless the web server seeks the OCSP response when the LE OCSP servers are down. It happened once when all the LE OCSP servers suddenly went into maintenence. Some of the domains had no valid OCSP responses with the certificates and FireFox deemed them invalid for the rest of the maintenence.