03-09-16 THAB:
"Destiny Update Recap: Earlier this week, Destiny underwent a small scheduled update. No changes were made to the player-facing Destiny experience. Once an Update has been released, Destiny Player Support monitors the #Help forum to ensure players are proceeding through the download process as expected. With this recent update, we saw an increase in reports of players having to re-download large portions of Destiny content, which equated to longer-than-expected console downloads. This is the result of a console attempting to verify all previously downloaded content. This includes the base game and all Destiny Updates/Hotfixes. If any issues are found, or the verification process is interrupted, all previous content will be deleted and downloaded again. To ensure that players do not encounter this often, we highly recommend using a wired connection when downloading Destiny Updates or Hotfixes. Additionally, if a player is experiencing network issues during the download process, this may lead to some content being lost or damaged. For more information, please see our Updating Destiny Guide."

Theory:
Did you try to "check your connection" to speed up your download?