We experienced an issue with the most recent Siege which caused a guild that did not opt-in to be matched with a newer guild of significantly lower strength. To be clear, this was an error within the game and was not intentionally caused by a guild.
When an odd number of guilds opt in, one guild that did not opt in will be pulled into the event so that all guilds have an opponent. We are making corrections that should prevent matches between guilds of such different strengths, like we saw this weekend.
Going forward, if there is an odd number of guilds that opt into Siege, the lowest ranked guild will be brought into the Event, even if they did not opt-in. Then, all guilds will be matched against a guild of similar rank/strength.
We apologize for the frustration and will be sending rewards to the affected guild based on where they should have been ranked. Thank you all for your patience and for bringing this issue to our attention.