Fatebringer actually drops anywhere in the raid. It's more rare than the scout rifle and Aeth Epilogue but not as rare as the Praetorian Foil Fusion Rifle or Praedyth Timepiece arc-pulse. Last Word is 100% RnJesus for now until it pops up at Xur, which it will one-day as all non-bounty non-raid exotics are on Xur's loot list based on what that one guy did with his clock-settings. You can look at its stats on my toon, think I still have it equipped :0