Hi,
Kingdom imbalance always existed since there are 3 kingdoms (at the start too), the problem now is that there are less players, and is more evident.
As suggestion I would start to introduce some real incentive to play this game. In fact it's open by almost 1 year and who have to start is far behind. Ofc this is how it always worked, but I would simply the life of new player until lv 60. About that there is no market for low lvl upgrade items, when I was lv 30 i could upp things by my self, now items doesnt exists (at least in Chunjo and Shinsoo). And more important than everything simply the exp process for the PET. I was in a guild full of lv 60 players who were stucked there to exp the pet, than got bored (playing 1/2h x day doing the same thing) and quit, and I saw this happen over and over in the past too. Is so essential to make this thing that hard ??? I would say the game is way harder after few lvls (75+), but at least is funnier.....