It's difficult to define "reasonable". What is reasonable for someone might be being able to speed run through a dungeon, while for another person reasonable might be simply being able to clear it.
If such an option were to exist, it would be abused terribly.

I can understand the frustration of not being able to finish a dungeon because one player is not pulling their own weight or geared appropriately, but to play devil's advocate, why is it that the healer should be the one to leave so you can finish the dungeon? I understand they were not skilled / geared well enough to heal everyone, but why does it mean they should be required to leave? Although selfish, such a person could say "Maybe the other people should leave if they didn't want to be in a party with me / don't like my playstyle."

Did you / someone else in the party give them advice on how to heal and the mechanics of the fights?

I'm not defending the healer in your party, just explaining what someone in their position might think / feel. There are many people who have never played an MMORPG before and struggle to get used to it for a while.