[whswhs]

I'm going to say again that the negotiator should also have Administration. They aren't just dealing with the hostage taker; they're dealing with the law enforcement organization that's waiting to take action.

As for Acting, two things: (a) Acting is the primary skill for cultivating a persona, which is surely in a hostage negotiator's professional repertoire; (b) a negotiator might want to have a cultivated ability not to react, which is kind of a narrow subset of Acting.