First of all, I agree with all LiadansWhisper said.

Now to me, it's not so much about why wasn't that whm able to save himself, but on why it happened. In my experience, if I get the littles on me it's because DPS is screwing up bigtime. Yes you could maybe save the situation from someone's fails, but sure blaming someone for not doing that is crazy imho. Yes, an healer can do more then just heal, but if the DPS doesn't even bother dpsing, why should you?