Diplomacy because you might have to persuade the troops to attack overwhelming odds (or something nasty, like a dragon). If you're an evil priest of an even more evil god (like Bane, the old tyrant), they're afraid of you anyway. IMO, Intimidate is to make people do things by seeming more of a threat as you really are. If you, the meek priest, tell your troops to "go and attack that black dragon, or you have to deal with me", the ruse could fail and you suddenly have half a hundred guys in front of you who much rather attack a boastful cleric than a beast with a mouth as large as you......