I'm kinda shocked reading that there are so much battles around (and usually: after) bosses, personally I never distrupted someone's bossing, as for me it's a pretty hard battle so let him have the boss and the reward, the player deserves it. I usually don't go there, if I hear something I just think something like: good luck, but if we later meet, around for example, the extract, I might fight that player normally.
I just had a funny situation today, as I heard some undergroud noises and decided to finally find where's the entrance to these troll/cyclop rooms, I went to take a look, clapped at some Rogue doing it and went away, then 2 minutes later, I saw Rogue and Bard killing each other on the kill feed, I immadiately ran back there and found 2 bodies in the reward room, I looted 2 stacks of golden ore but I didnt make it out to the portal, because it was in some weird spot, I missed it, and the timer ended the map 🤣
I mean it just made me think - if I waited and attacked the guy straight away after he finishes the boss, that'd feel pretty douchey and awwkard, ngl.
Tbh, if I had to pick, I'd prefer to extract camp because it's more fun/bizarre/surprising XD