I had a BSOD on that... I believe my exact rant went along the lines of "So their one redeeming feature is that if you don't hit them, they don't die? They actually have to spell that out? Are there monsters that die regardless of what you do?"
Some powers in 4e still deal (drastically reduced) damage if they miss. This protects minions from getting sure-killed by someone using a power like that.