Also, I think the problem is needing a database to serve content, not to generate or store it. Many people would be happy with a system where the database is needed only by the author, generating static pages from the database content and then serving those even if the database is down. I even wrote a bunch of scripts to use Wordpress as a static site generator, before I switched to Pelican. With a little more work I probably could have turned that into a turn-key solution that would still insulate readers from database problems.
yes - this or w3tc - either of them have an enhanced disk cache that keeps the generated html for each page on disk and apache/nginx will bypass php if you have the rewrite rules in place.
Existing platforms suck. Some of them have plugins or hacks for this, but mostly it's the fault of the developers for not making their tools more robust. So my comment is partly to blog users, partly to blog developers.
I use Jekyll, but when I tried teaching it to someone I realized that the learning curve was too steep and switched them to Wordpress.