Might be cool to have them know they were attacked by something as well to be honest. NKs should be slightly more informed over other players in my opinion. So they would generically be informed of being attacked by an Archer/Knight/Alchemist/Hunter’s Mark/Cult Leader/Assassin (maybe one more that I’m forgetting).
This would enable them to react more quickly to a thunderdome and react accordingly. Alternatively, they would know that scum now knows them, so they play to that or try and create a scenario where they “self-healed” or beared or the like. It’s still a guessing game for the exact scenario for them, but they can anticipate slightly more. It’d have to be clearly stated in a passive though, since it’d just apply to NK’s.
In addition, NKs could use a buff now that it’s been raised to 18 players.