It’s telling of how the group can handle the first pull in the dungeon.
Because sometimes it’s the healer. Sometimes it’s the DPS, sometimes its both. Sometimes it’s the tank too. If your healer is the weakest player, which should happen approximately 20% of the time, the dps will be healing themselves and they won’t be pumping. If the dps die, they won’t be pumping. That doesn’t mean that the healer can’t time a 20, it means that they can’t handle 15 mobs.
This is besides the point. If the healer is a disaster, vote to leave and one of the dps will agree with you.
It’s very simple. If 80% of the group wants to stay, you’re the jerk for leaving.