The other day I was in a group heading to elite Running with the Devils, and I was joking about how many times we would die. The cleric half-jokingly asked me if I was worried about my healing skills. And I said no, if your healing skills are good, we'll die only a few times. We wiped. Then we redid it with a stronger party, 1 or 2 deaths, and I told him that means he was a good healer.
And sometimes everyone screws up. Last night I was doing an elite Coal Chamber. It was in the evening and I was tired but not quite ready for bed. We went in with 5 and I popped my Onyx Panther hire because we had been talking about the hires... and you already know what I did wrong. After the quest someone told me and I was apologizing all over the place -- a real bonehead move that was, but we all do it from time to time, and need to remember that we're all human (even if we're elves or warforged..)
If I had someone ***** someone else out over a death due to anything but sheer negligence -- such as being warned not to do something and doing it anyway -- I'd just squelch them on the spot and drop party as soon as that quest was over. Life's too short.