Whenever the message pops up, I would ask if anyone needs an explanation for the bosses. If nobody pipes up, I would assume they at least looked up a guide or have done the dungeon before. Though, I did have a few run-ins with players claiming to be alts, but then turns out they were lying about it. I don't mind helping out, but being lied to is infuriating. :p
However, the dungeon trash needs not an explaination since they are more or less the same. If I'm tanking, I'll adjust if the group isn't well-geared, but will pull enough that the party is moving at a decent pace.
