Turn off all the gay lighting and shadows in the advanced options. Could also adjust CPU affinity in the eqclient.ini
Edit: Looks like they already have CPUAffinity in the client updated to use more cores. But doesnt look like its working. When I check CPU cores in task manager its only using core 0. Try opening task manager > Details > find eqgame.exe > right click set affinity and add some more cores. Also looks like you can set the CPUAffinity settings in the eqclient.ini to -1 maybe. The settings were all over the place in my ini file so be sure to do a find to track them all down.