It looks like SE has a bit outdated(or at least incapable of population influx from other games) server infrastructure, considering they have even hardcoded 15 minutes timeout into client side. As far as I remember, they are not yet trying out those AWS or other cloud server services yet. Maybe it's time to invest into those options? If SE's intention is not giving out any more compensation, maybe invest on those cloud infrastructure then reduce the portion of cloud infrastructure when the rush period seems to be passed.
Of course, those cloud services would charge a lot up front since it's an emergency purchase. But the EW hype hasn't completely dwindled yet and the dinosaur of MMO is still crumbling. It's the best way to invest more to obtain loyal customers who have track record keep returning to their favorite game for more than 10 years.
I know there's some grudges on Korean companies Japanese people has. To be bluntly: Panasonic+Sony+all the other Japanese tech <<<<<< Samsung Electronics these days. But you need to learn from the competition. LostArk is a Korean title and they are doing extremely good in their domestic market as well.
https://namu.wiki/w/2021%EB%85%84%20%EB%A1%9C%EC%8A%A4%ED%8A%B8%EC%95%84%ED%81%AC%20%EC%9D%B4%EC%A3%BC%20%EB%8C%80%EB%9E%80
(Language: Korean. Try with your luck with translator if you can't read Korean)