SASS + Compass - File Structure and @Import order
Your way works, but it is not very scalable, since you have to compile all the sass files every time you make a change, this is time consuming when the project gets bigger.

here you watch all the files via grunt/gulp, but only compile the _watchables, the _procompiled file is compiled upon start of server only, not during file watch.

when building for production, use build.scss to build the final css file, the build contains the watchables and precompiled files.

the _globals file will contain global configurations, styleguide variables, and functions/mixins. the global file does not have css in it, only utilities and functions, and is imported in both watchables and precompiled files.

Structure

.style
├── build.scss
├── _globals.scss
├── _watchables.scss
├── _precompiled.scss
├── vendors
|   ├── index.scss
|   └── _bootstrap.scss
├── helpers
|   ├── index.scss
|   └── _variables.scss


build.scss

@include '_globals.scss';
@include '_precompiled.scss';
@include '_watchables.scss';


_precompiled.scss

//contains vendor files and other unchanged scss files.
@include '_globals.scss';
@include 'vendor/_index.scss';


_watchables.scss

//contains the files you want to build everytime you save
@include '_globals.scss';
@include 'pages/homepage.scss';


any index.scss file

//include everything in the folder.
@include '_bootstrap.scss';


I developed this way while working on a big project with my company, the build time got reduced from 8ms per file save to less than a second. i was compiling only the pages folder in my watchables.scss file, since the rest of the files are almost always stable, but sometimes i include a component in my watchables to develop the component then put it back to the precompiled file.