This is a suggestion of course but it had to do with the topic of server merges and a stable population.
Perhaps this is the weekend and winter holidays and so my numbers may be a bit off. I'll look farther into the details. I have watched and counted Sage World Battlefield and the GNW and come to a preliminary conclusion that 3-4 servers together is not enough. I will reply in two weeks if the numbers continue to trend in a negative manner.
So my thoughts are instead of 3-4 servers merged together a total of 9-12. People who have spent money into the game will * around and those who find the game enjoyable will too. It also has such a large population that people will always be challenged at the time of GNW and there isn't going to be a garunteed victor (Or well shouldn't) 9 tails will be so easy to defeat that is for certain but doesn't 9 tails increase in power and health every time he is defeated. So perhaps we up the scaling and strength of 9 tails.
When you merge 3-4 servers it is very active for the first week or two, but at some points, you'll notice a diminish in player base in GNW and Sage War. Goes back to being a server that just opened.
That's what I mean. If they merge 7 or more servers, the game will have more competitiveness.:)