Loading small resourcepack causes unexpected delay

My resourcepacks replace three entity textures and one background texture, totaling approximately 24000 bytes (ie., not very large). I have a default resourcepack, and two others that are loaded in specific Multiverse worlds; the lot are managed by WorldResourcepacks. At that small size, the downloads are trivial (and if I understand correctly, are cached after the first download). But there is a 9-10 second delay while any of my resourcepacks is installed, either on initial load or when I traverse to a world that uses a different resourcepack.

What I expected to happen was...:
MC/Spigot login with no server RPs takes approximately 2 seconds. So my expectation was that my few textures would be loaded after that, requiring a few milliseconds at most.

What actually happened was...:
There is a 9-10 second delay while any of my resourcepacks is installed, either on initial load or when I traverse to a world that uses a different resourcepack. As a guess, it seems that the vanilla resources are reloaded whenever a personal resource pack is loaded.

Steps to Reproduce:
1. Connect to server.
2. Wait while resources are loaded.
3. Change worlds
4. Wait while resources are loaded.
5. Repeat (3-4) ad nauseum...