EQ2 FPS issues with multiple clients running

I'm having FPS issues in the Rise of Kunark expansion zones and I thought it was a new problem but turns out its always happened it just wasn't noticeable.

When I start a second instance of EQ2 I take a 20 fps or more hit to the first instance. Prior to the RoK zones I would run at 60 to 80 fps so the lose wasn't something I was noticing. In the RoK zones I'm running lower framerates on the first client so when I launch a second or third I'm dropping down into the teens at times even at the high performance settings.

In the past when I've run into these issues boxing a game I start looking for the bottleneck, throw some money into my system and problem solved. The problem is there is no bottleneck. CPU usage never goes above 30 percent which is the weak link in my system. Cores are still showing parked even with the option checked in EQ2 options to use multicore cpu's. It appears the game simply won't use the system resources I have available.

Currently I can 2 box at "extreme performance" setting (which is ugly) and launching a third client makes the game unplayable in the RoK zones. The problem occurs launching with ISBoxer and without so it's not an ISBoxer problem.

I'm not sure if this is a problem with poorly optimized RoK zones and the situation will improve ( but would hate to pay 3x CoE expansion to find out it doesn't) or if it's a fixable problem and I'm just looking in the wrong places.

System - i7 960 3.4 - 680 GTX 4 GB - 16 GB DDR3

Criels I am trying to do some performance tuning on my computer at the moment. Not sure if you ever found a fix.

I have 3 game instances all running at 2560x1440 on the computer in my sig.
I know that EQ2 loves single fast cores so I turned off Hyper Threading and designated 2 cores per game instance. This didn't seem to help with FPS much. I can run at High settings with all shadows disabled and get 30-40 FPS in the old lands and Faydwer so far.

I tried setting the resolution lower (1920x1080) but the FPS stays the same. This points to it not being a graphics card issue and my two cards don't go over 40% usage when playing.

My CPU and cores all hover around 70-80% the whole time while playing. It is strange that your CPU remains mostly idle.
I am sure you have tried turning off shadows but that was the biggest performance boost for me. It is a real shame as shadows add so much immersion to the game.