So like I said, if you think leaving a key is totally fine for these reasons, why would a deserter debuff matter to you? You had good reason to desert, and the buff doesn't do anything except let other people know that you deserted.
Basically the buff's function would be to let other potential groupmates know that you think it's ok to leave a key under certain circumstances. Why should that information be hidden from them?
The system wouldn't be perfect, no, but it would be better than the current system where people who are interested in completion get routinely fucked over by people who consider themselves a higher class of player.