Keep in mind that they don't have crossserver sage yet, it's 1.0. Right now, unless the server is really populated, like 200+ active people at once, they all will be thrown into 1 battlefield, no matter if lvl 40 or 70. Since their server started like 1 year after english version was released (they are 1month old or so), we can assume they will progress in similar way. In that case its about 6 months until they receive xserver sage. Even then, whether to hold your lvl back or not will depend on his/her current bracket. For example at my server bracket for sage there are no. ~300-400 servers, and even while I was 83 I was already in the highest bracket with 87-90lvls. Don't get me wrong, general idea to slow leveling down (not doing plots/wanted) but still attending 9tails is a good strategy for farming, but - like with everything - other factors need to be taken into the account.