Yes, sure in hindsight but that underscores another problem. The complexity of creating a system and then putting in all these safeguards. Or you could just run with other players where you can trust them to not be a douchebag and not (spitefully) brick your key.
One of the primary reasons why they are so hell bend is because they want "justice" or vengeance. But because of the anonymity of group finder, you're very unlikely to run across the exact same person twice in a row (except in extreme circumstances).
And a whole host of issues come from various scenarios. If the group doesn't have the DPS to even kill the trash before the first boss or struggles with some mechanic why are any of the players beholden to stay? Why should Bob be punished for poor gameplay from the other party members? Is it Bob's job to teach them the errors of their ways? What if they don't want to learn from Bob? Maybe their way of playing the game is less try-hard (but also means this particular dungeon run is going to last hours).
No penalty as in no key degradation? Yikes that's a bad one if you think about it. Hey guys we're not going to time it, let's vote to abandon and restart (since we don't lose a key level). Hey guys, we couldn't pull off that MDI level strat, let's vote to abandon and restart. Hey guys we forgot to lust/heroism on the first pull (a triple add pack), let's vote to abandon and restart. And so forth.
Yes but you're missing the point I was trying to make: Until you get to 1k keys done (or some other high number), then you are "FORCED" to stay in keys because you leaving would greatly affect your record.
Additionally, without any context, a person with a 50% leave rate (did 2 keys and left 1) looks horrible but contextually that might have been a legitimate reason and because their total number of keys is low, they are less likely to be invited in future runs.
Same issue as before. Percentages don't work very well because it penalizes those who don't run many keys. A rolling average over the last few days/weeks also doesn't work very well because of specific cases where players can misinterpret the data.
Take someone who is pushing ultra high keys: They may leave a ton of dungeons over a week as they try to push keys because for them it's about being able to time the key and as soon as it becomes apparent that they can't complete the timer, they bail. And that's OK for some groups and players because that's their goal and they are only looking to play with other similar minded players.
Honestly, it's an issue of the group leader not screening their candidates well enough. When goals don't align, you're going to run into problems.
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Holy smokes that's even worse! Bob wants to leave this group but doesn't want to take the penalty of losing his score. So he's going to make someone else leave first. Should he be passive aggressive about it? Or maybe he'll just play super aggressive and cause a lot of party wipes.