Good point. Although I'd say that any such attack like that is still unlikely to cause the entire site to become instantly unresponsive (or to serve static error pages as other people have suggested; personally, I just never got the site to load). And similarly, it would not be expected to come back to normal operating behavior a few minutes later. So yes, I'll grant you that you can DDoS even large sites without needing pure brute traffic, but it still doesn't seem particularly likely here.