Another update by the Grumpy Elf:
MMO-C recently posted about the raid completions based on the data they were capable of collecting. It is not entirely accurate, and they admit that, because it does not track everyone in game. They can only fetch so much data, it is to no fault of their own. They can however scan for achievements, and they are using those to track it as best they can. This is a very good way to do so even if the possibility of someone not coming up in the achievement scan is completely possible.
So while their numbers might not be 100% accurate I can believe that that are a reasonably informed guess. Enough so that I am willing to play with those numbers, because they are all we have, and I'll consider them close to accurate, + or - a margin of error of course. That margin of error is most likely small however.
They say that there are characters not in guilds that are not counted, but then again they most likely count characters multiple times as well, even if they say they have taken every effort to count only "players" and not characters. The reason for that is because you can disable being tracked by not sharing achievements. ...Read more.