I think an encounter like this would be fun:

At the end of a raid, you have two bosses to fight: A high damage and healing caster type and a heavily armored, high damage brute.

The logical thing to do would be to separate the two and take out the caster first. But lo!, the two stick to each other and the brute is spamming intimidate! The combination of high AC and HP, plus reinforcment from the caster will make this a long and dangerous fight unless the heroes can find a way to neutralize this new threat!

NPC Intimidate:

The way I see this functioning is just like PC driven intimidate, but with a few modifications. The brute (a sword & board user) would intimidate once threats are in range. This would be a d20 + intim modifier check vs the players' HD + Wis mod. Upon success, the players' targeting halo would switch to (or activate on, if not already active) the brute and place a debuff on the players. Since the caster would stay close the brute, damage would be redirected to the brute. The players are welcome to change targets at any time, but the debuff would switch the halo back to the brute every second. Thus the players will have to constantly switch targets or find another way around this. The debuff will persist for 12 seconds after which they get a 3 second reprieve and then the brute intimidates again!

Strategies:

Brute force: break through the healing rate and just DPS the brute to death

In and Out: players break away from the brute until after he intims (will have to sacrifice one player) and beat on the caster during the cooldown

Immunity: Turbine can institute an item or buff that helps prevent or make the players resistant to this effect

Player designed: Through vigorous play testing, players can find an alternate strategy. Perhaps the brute has an animation that can be interrupted through certain effects or abilities