By far the most common MITM attack is through untrusted WiFi networks. That's when SSL is most valuable to the user, and also when it's easiest for an attacker to block access to CA servers. Other kinds of MITM attacks are so much less common they're barely worth talking about in this context.

IMO, an adversary that can extract a cert using Heartbleed and set up a MITM should also be advanced enough to block some IP addresses.

I'm confused by the rest of your comments about Gibson. All I said about him was that he continues to generate hysteria without providing details or citing prior discussion. The only things I'm accusing him of are things he is still doing today.