Maybe some adjustments in the ranking could be made in the future when more and more users will get the legendary rank.
I think the rank should be tied more to the activity in the forum, with, of course, some ties to merits, but what defines a user as legendary is the resilience in posting in the forum valuable content, so I guess being activity more difficult to grind rather than merits, should be taken in more focus.
I don't think future ranking adjustments are a bad idea. I imagine that every 10 year old Legendary on this forum could be given a new rank in the future
"Legendary II or something" especially if they have achieved a certain number of activity and merit. That rangking should be achievable for every loyal Legendary user to be active on the forum, but it might be hard to expect it for the current forum but more likely to be integrated in the new forum later.