I've pulled during cutscenes before, but it's usually an accident. Sometimes I get a little trigger happy and forget to check if everyone is present and accounted for.

If you get the "new player" warning at the beginning of the dungeon then waiting for cutscenes is just common sense; if you don't you're a jackass. If no one is new but someone's still watching cutscenes then pulling before they're done isn't a huge deal, imo.