Nostalrius Begins - Quality wow vanilla realm (1.12)

Between Christmas and Newyears eve I was playing and everything was perfect. But playing here on the 4th of janurary the game feels much slower.

Autolooting causes the loot glow to stay for up to 3-5 seconds after looting.
Spellcasting sometimes says "failed" but casts anyway.
Damage seems to register up to 1-2 seconds after a spell has hit an enemy.

Has there been a patch to the netcode or something? I'm pretty sure the game was better last year.

Increase of the daily playercount is mostly the issue.