I kinda agree with the WP people that this is not really an exploit. If you call a script that does a few seconds of processing, and keep calling it, yes it will take down the server...
That said it can definitely be mitigated by checking for this kind of request explicitly and not letting the same IP keep requesting the URL (plus caching, etc.) Maybe it's an argument for WP to integrate some of the features of 'firewall' plugins.