If duty finder is the main cause of this login server congestion why hasn't it been turned off for the time being.
Because it is required for many important quests (Story/Class/Relic) AND is end game for those who are 50 on all classes.
If they disable it all you can do is fates/gathering and non-instanced quests (which is enough for leveling to be honest) but it would mean the players won't know what is really going on since it will feel like a single player game with a chat.

They did chose the lesser evil and restricted login to the servers. I'm not saying I like it either but well...you can't do anything about it whether you quit or not.)

My only hope is that they fix this by Wednesday.