[platform]/Account/[account]/Character/[character]/Activities Not Returning Correct Raid Completion Flag?

We will have to look into that - BNet no longer uses the /character/Activities endpoint for any purpose, and thus it has been practically deprecated (though not officially deprecated, which is a point that will likely soon be corrected). It is very possible that isCompleted state is not returning as one would expect. I have filed a bug to investigate the issue, but if I recall correctly the isCompleted flags on the Character/Activity endpoint isn't telling you whether you completed it, say, this week: it's telling you whether you have ever completed that activity. (which is less useful than knowing whether you completed it for the current week and probably isn't what you wanted) The most ideal place to look for raid completion info is the MyAccount/Advisors endpoint, which unfortunately is a private/auth required endpoint currently. (This fact has not stopped people from using it before, but we cannot provide official support for it)