I think dark creatures play more "normal" to keep from being meta-gamed. They Are Monsters assumes the player-base is going to treat you fairly, which 90% of the time is never true during a random conflict. Of course not all the time, but even subtle details people will take as a whole clue to solve the puzzle they already know OOCly to bring IC. I do not think your point is what I am saying, but my point is role-playing different from a group (whether human, elf, orc, dwarf, ect) only brings trouble usually for the dark magic player. It is up to the ET to bring players conflict-driven story-lines. I would never play a dark magic creature to entertain anyone other than myself ULTIMATELY. And there is usually little time from moderation to effectively help dark magic players have some resources against the common tropes of power-gaming and meta-gaming in all ways that bring advantage the average player.
the common player says, "zug zug zug"