I understand that Legendary can probably write more quality threads but I think the overcap merit is almost trashed merit since they don't need it. Don't you think is better to use it on Newbie-Hero Members?
I'd rather see merits sent to Legendaries (whether it's 24% or 50% or whatever) than stay unsent. Those Legendaries might spread it further.
Keep in mind that (a) merits are not scarce - we might be too lazy to send them but there is no lack of them; and (b) the primary purpose of merits is to award them to good posts and ranking-up is just a bonus. Nobody "needs" merit to participate in the forum.
Also what xtraelv said. Don't overthink it. Apply to become a merit source if you haven't yet.