As a narcissist, I noticed that quickplay host character lines never play when you get a killstreak. Lines such as. “So you slaughter the guilty too.” “I think Grimgi’s having a fit, effective though.” “Fine show sir, no heretics safe today.” Ect.
These voice lines are the typical one-offs with no other responses. They differ from the killstreak dialogue “Keep your elbow up, your guard’s open.” “You, dare, thank you Kruber for your advice.” “As you should Grimgi.” Ect. The 3 character back and forth praise dialogue still works. As does dialogue when you get a critical/first blood. Your “Barak Varr Handshakes.” Still work.
When joining a game, and not hosting, killstreak single character spoken lines will play.
I had originally thought I was doing poorly because I wasn’t using swift-slaying, and that my attacks weren’t fast enough to play these lines. As it turns out it is entirely host dependent.