Kartia is super easy, gives huge exp, and you can basically watch your favorite series while doing it. (either using macro or saving vit) It is good exp until level 102. I think in the new update, with the reworked xp penalty system, it should be viable even after that. So, good luck waiting!
Because we are not developers, we operate the game as the original developers (NCsoft KR) create it and we have a very little room for adjustment. And the devs don't think it's necessary, otherwise this would already have been changed.
If you exclude L2 Classic (which doesn't have instances anyway), Korean L2 doesn't start a new server since 2007 IIRC. They merged 8 servers in 3 some years ago.