I played the weekly heroic strike three times and the nightfall once this week. During two of the strikes, I encountered a captain (4 arms, swords, yellow health bar) that was invulnerable. When that happened to me the first time when doing the weekly heroic strike, I started opening fire at it with the Corrective Measure at a good distance. Should have stopped or at least slowed it down significantly. My gun fire had no effect at all. The captain kept coming straight for me and insta-killed me. At first I had thought I hadn't hit it, but I cheesed that strike (nightfall this time) later the same day from under the metal platform at the far end of the boss area and I repeatedly and deliberately shot another instance of that captain from there with primary (VoC, solar), secondary (Epitaph sniper rifle, arc) and heavy (Corrective Measure, void) weapons, I did hit it, and I did no damage whatsoever to it. WTF? Does anybody else have experienced that?