There was a big push at the last night of season (EU), the ladders and online trackers were bugged around midnight. The most accurate cutoff would be represented by the latest snapshot of the accurate ladder (the one closest to the season end) calculated with the accurate faction percentage (unknown factor, the percentage of alliance and horde split on total players can only be guessed atm, some websites take a guess around 59% Alliance 41% Horde, some websites directly calculate on 50%-50% basis).
For arenamate, I could say that 2610 alliance EU is too low, if you check leaderboard snapshot around 00:30 CET, rank 563 (this is what arenamate claims as alliance glad cutoff) is at 2651 rating. Therefore, even though arenamate's 50-50 guess has the chance of being accurate, the wrong ladder information causes it to confuse the rating (down to 2610).
The trackers went down around midnight, so we have 6.5 hours of darkness, and only a few people know what happened during that last push period. The glad cutoff could even be 2700, because it depends on the rank. All I can say for sure that 2700+ is safe glad tbh. People above 2650 have a chance of getting glad as well (speaking for eu alliance)
On the other hand, we should also remember that there will be disqualifications. I have seen a lot people miraculously getting +700 +800 rating at the last night. Now it is possible that they could have farmed it legit, but it looks really suspicious, considering that most glad-range players were actively playing throughout the season.
The healthiest way to check your cutoff would be to consider the worst case scenario, apply arenamate's 50-50 approach to a more updated ladder (most recent was around 00:30 I think), check the rank, and the rating at that rank, you will have an idea on what happened 6 hours before the deadline. If you really want to go crazy, you could calculate the rating increase rate (compare 1 day before with the last day's increase, and use proportionality to approximate the potential rating increase in those last 6.5 hours).
If somebody has any updated information (dq, another recent snapshot etc) please feel free to correct me.
Edited by Warmonger_Skulm, 18 December 2016 - 12:49 AM.