I've been hit several times by being on the front page. By my estimates, that worth around 700 requests per hour (http://shkspr.mobi/blog/2012/11/whats-the-front-page-of-hack...). I don't think that's excessive and using the above, my bog standard WordPress install has never fallen over.
*I'm aware not all stories are submitted by their writer - but I consider the above to be best practice for any competent website owner.
On the other hand, if HN could frequently check if a page is still responsive and, if not, then show a cached version until it's back up, that would be awesome, but given the underlying software doesn't get many updates anyway, I doubt we'd see anything like this soon.
People would be better off optimizing their site/server. It's a good lesson to see what happens when your site gets a boost in traffic.
It's better to struggle with the hacker news treatment early on and learn to cope with traffic spikes than have the same problems when your site gets mainstream coverage.