One thing we've tried to do recently with our Sass is to leverage Sass' extend functionality for defining static CSS rules we want to use over and over as an archetype. We tend to use mixins for anything we're passing arguements/variables into. See https://github.com/edx/edx-platform/blob/master/common/static/sass/_mixins.scss for a good example of what we're doing.

@caesar2164, would you mind making these extend definitions rather than mixins (it'll require you to also change your reference syntax elsewhere to @extend from @mixin)?