In general, when we set a mission that requires "Wins", we assume that a player will have a 50% Win Rate. Expecting 10 Battles to be needed could be a significant amount of time depending on the experience, as average battle length is 10-15 minutes. On that assumption, it could take as "little" as 50 minutes of playtime to receive 5 Wins in a row, or as much as two and a half hours of playtime to get 5 Wins over the course of 10 Games Played.
With the inclusion of Scenarios, this could be 5 runs of Narai which is nearly a 100% chance of winning should you have a few other players that enjoy Scenarios.
50 Minutes to 2.5 Hours of playtime in the ship over the course of 27 days doesn't seem like an overly large ask.
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I've inquired about the inclusion of an "Or" condition that could be set for Co-Op Wins, but by the time metric described earlier the expectation would likely fall in the mid-point of around 1.5 hours. That would be about 18 Wins in a Co-Op setting.
Given that the mission has such a wide variety of options already, I don't want to get anyone's hopes up. Please assume that the mission will remain as-is unless told otherwise.
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As to the quality of experience, I can only say that I've enjoyed playing her the few times I've done it.
Boggzy recently recounted his experience in another thread as he has had only great games with her.
Link to his post: