How can they efficiently do that? Will they send a request to Google/Mozilla/Firefox and asks if cert ABC logged?

I see two issues with that:

1) the browser vendors know each site and subdomain I visit. This seems to be a privacy issue.

2) every new visits adds a lot of latency because they need to check the certificate every time I request a site (now it becomes: dns, ssl handshake, cert check, http transfer).

3) when the cert check server is down, what is supposed to happen? Fail every ssl request? This adds a new point of failure. Just allow it? An attacked could black-hole the dns or block the IP address.