Epilogues are generally released after the game's main story has been completed. They often offer insights into the game's events, or resolve plot points that were left unresolved. Players usually have the option to replay the game's main story from the start with their current party and equipment.
Xenoblade Chronicles' epilogue is no exception - it is a self-contained story that further expands on the game's events. It is also one of the longest epilogues in recent memory, clocking in at around 10 hours.
So, if you're a fan of Xenoblade Chronicles, then absolutely, the epilogue is worth playing. It's a great way to see more of the game's world, and to get some closure on the game's story. However, if you're not a fan of the game, or if you simply don't have the time to invest in another 10 hours, then you may want to skip it.
