Listen, facing Khagan, the Ettin lord himself, in the Cave of Thunder, it was a blast, though, I have noticed he doesn't have a Second Chance Chest after defeating him.
The survey to request to add a SCC to Khagan is filled out as follows...
1) Is the boss in question at the end of a long instance? Well, reaching Khagan was no easy walk in the park, for there were hordes of Ettins I've had to plow through, & it surely took long enough to get to him, so, yes, he is at the end of that long instance! Check!
2) Does the boss in question have any unique loot? Well, I did read that his weapon, the Ettin's Pauldron, is unique to him, because it's pretty much relatively close enough that the weapon is from of his kind, so it does counts toward as his unique loot drop, therefore... yes, he does drop unique loot! Check!
That's the survey! Hope Khagan receives his Second Chance Chest sometime soon.