I've renamed "Master feature" to "Epic" and use this artifact for large user stories (releasable value that is larger than one single story). Within the Epic I create multiple stories. This story breakdown is relevent to the developers but when I'm viewing the board with releases I want to see all the user stories (those that are NOT contained by epics) alongside the epics because these are all the release-able work-items. The reason I want to see them on the board as opposed to in a report is because it allows me to prioritize and move around items based on release planning.