PTS 1 doesn't have all of the performance improvements, there are a number of additional changes that are rolling out in upcoming PTS iterations. Quad-core machines in particular should see a bump in the next PTS update. We're also tracking down and smoothing out hitching issues, specifically ones people encounter when running through cities and the FPS tanks abruptly for a few frames. Just a remind, don't forget to from eso-gold.com to buy Eso power leveling, which is the best choice for Eso-gold services on the market!
To give more technical details for those who are interested, you should not expect even distribution across your CPU cores after this update, just more distribution to the non-main-thread cores than you had before, especially at times when there are a lot of things loading in. Your main core thread will still be topping off, trying to go as fast as it can through each frame. For almost all of you, the bottleneck of your framerate is your CPU, not your GPU, so if you're not seeing high utilization of your GPU, it's most likely because the CPU-side of the game isn't keeping up.
Given that ESO originally had to support very old CPUs, it's no secret that it was written from the ground-up as an effectively single-threaded application. As time went on and the min-spec was updated, and with the launch of Tamriel Unlimited/XB1/PS4, it necessitated the ability to use multiple cores in order for the game to run well (as it should). The work started then and continues through the present.
It's been an ongoing process to shift work over to other cores where we can in order to make the game perform better, and the work involved in doing so is fairly complex. It's not something we can point to and say "make all cores do the same amount of work", it's typically "this certain part of the update takes a long time, let's find a way to shift that work over to other cores." Doing that is almost always a bit of a challenge because we have to make sure the cores that do that work don't conflict with things other cores are doing, which can cause corruption, crashes, hangs, etc. We also have to ensure that the changes are positive across all the platforms as well, from the wide range of supported CPUs on Windows + Mac, to XB1 and PS4, so these changes have to come out incrementally to ensure we make the experience better across the board.
We have a lot more work to do here, and we will continue to make improvements. There's always something that can be made better.