I ran across this in the beta, and it's still here in the full game - the fallen captain public event in the Forgotten Shores. He's a level 5 fallen captain ultra that has more stamina and umphh to him than even the Celebrant of Oryx in basement of the 2nd warmind recording building. My buddy and I yesterday (both level 25 with some good weapons) could barely break his stupidly strong shields, much less do significant HP damage, before the shields would completely regen and he'd start running again. We do level 26 missions and strikes easily, and this guy took everything we had and practically shrugged it off. There is NO way in hell some level 4-6s are going to take him down, even if there was a dozen of them or more working in concert. If 2 level 25s can't take down a single level 5 captain, something's seriously overpowered for where it is. Bungie, please take a look at this and either explain to me why it's nearly impossible to complete or fix it.