I hand-modified my eqclient.ini file, and zoning improved quite a bit. A lot of lag in populated areas remained, however.

I deleted the eqclient.ini, started EQ, then pulled over all customizations from backup and logged in. Amazing difference - no serious lag even in areas like guild lobby, so fingers crossed.

Also, during beta and right after DX11 was introduced on live, my spectre pets would appear shiny silver. This remained after hand modifying the eqclient file, but they are now "back in black" so to speak after having the file rebuilt. Fingers crossed...

Thanks for posting this info Fanra.