We had a situation in Halatali HM before they fixed the Instance patch where our WHM was dying at the end of the second phase of the last boss fight. Not their fault mind you but they ended up dying. I was on BLM at the time and had to switch in healing mode to keep the tank and dps alive while they killed the Manticore (we had killed the THM prior to WHM's death). It was fun though scary with having to physick everything.