I'm currently keeping an eye on this addon. It's by the author of PhoenixStyle (who has not developed PS for a while now) who has returned to the game and is writing this new one. He plans to update PS too post 5.3. The idea of CombatReplay is to be able to do wipe analysis after each try. Combat & position data is used to recreate the motion and casts of each individual player in a sort of 'movie'. Looks like it could be really helpful!
Should be on Curse just after 5.3 has gone live.