this guy can be a pain ... another very easy way to do it is to kill Crota Blades, take their swords and rush to him. Did it with a friend yesterday he did not even resisted and we killed him in less than 5 secs. But if you are using guns on him it can take a while, he has a very high defense and the most annoying part, he disappears very, very quickly! So you need to kill him very fast. Also he does not only show up during public events, he can also spawn just like this.