gt2x - sorry we boned your experience. We did shift Asia servers from Tokyo to Seoul, with the intent that it's a near-neutral change for most players and a positive change for many players. That said, we definitely don't want to pull the rug out from players enjoying our game and this current shift isn't necessarily final or forever. As Asia player populations continue to grow, we are likely to need both datacenter locations, but we have to figure out how best to solve for cases like yours seamlessly rather than just randomly bouncing you between Tokyo and Seoul servers, which is quite a variable experience in your case.
Can you please do me a favor and let me know what your ping is to each server region via in-game settings? That would be helpful as we dig more into the data from our end to see what the full scope of positive, negative, and neutral impacts are here.