but this thread doesn't mention the required merits, only the activity.
Probably cause this thread was originally created as far back as 2013 when there was no merit points required to rank up, it was edited later with a link to the merit requirements for the different ranks;
Also, I don't get why Legendary should be within a range of numbers. Isn't this a little unfair?
Could be a means of adding a bit if drama to the rank as users are unsure if when exactly they would hit the unique activity points for their account to get to legendary status. It may be considered unfair to some users who have to wait really long to get to the the apex rank.