I think you need to focus on player count for merges not balance. If you need to merge a whole world set then do that.
Coming from hades you are merging a 300 player server with a 100-140 player server, why is asgard also not part of this which would then make around 1200+ peak?
Balance always changes, hades map has flipped dominant factions many times over the months.
Please try to make server merges hit as close to 1500 players as possible