Gradients require coloring for each individual letter (~8 additional characters per letter), so naturally the raw text of players' display names can get very large. This can snowball with many players. In order to prevent issues with Essentials, NameColor updates nicknames with Essentials when possible. On GitHub, I published a slightly more compact version, but unfortunately there's really not much that can be done on my part.
Even with that considered, the vast majority of a Essentials user file's size, even with a large display name and gradient is NOT from NameColor.
If you decide to try the plugin out again, please feel free to reach out to me if you encounter any issues. I'd much rather try and help you than see a negative review.
Latest version:
https://github.com/Wiicart/PedestriaNameColor/releases/tag/v1.11.2