This scenario was testet in Visual Studio 2012 with the Web Essentials extension.
Filesystem:
root\folder1\subfolder1\styles\main.less
root\folder2\subfolder1\subfolder2\styles\fear.less
main.less:
@import "../../../folder2/subfolder1/subfolder2/styles/fear.less";
Compile Error:
LESS: Couldn't load folder2/subfolder1/subfolder2/styles/fear.less (404)
Is it possible that LESS does not support multiple subdirectories?