We get pretty good
If the healer dies, Requiem Lant is the tank fault. We learn early in our dungeon running to work together as a more cohesive unit than what we worry about with the DPS, and over time and with practice, we get pretty good at it. Like the tank, if the healer dies, unless there is a backup healer to pick up the slack, the rest of the party is generally doomed to death as well.