EVERYONE, yes EVERYONE needs to make sure they go to their client.ini in their EQ folder and set ALL CPU affinities to -1. Like every single person playing Everquest. Yes, you reading this who didn't know you were lagging.
There's also some stuff you can do with your task manager process details for Everquest with CPU affinity but these two changes alone will fix bad lag for 95% of players. Basically EQ only runs off one core by default. Fixing this allows you to use all your cores and makes running EQ a complete joke.