It is a Prestige Class. You mean one a PC can take? I don't see how stirring up animals to attack would be like this; they don't naturally form mobs. It occurs to me that having a mob leader wouldn't make sense without a mechanic for mobs. I guess I'll start with crowds.

Quote Originally Posted by D20SRD

Crowds

Urban streets are often full of people going about their daily lives. In most cases, it isn’t necessary to put every 1st-level commoner on the map when a fight breaks out on the city’s main thoroughfare. Instead just indicate which squares on the map contain crowds. If crowds see something obviously dangerous, they’ll move away at 30 feet per round at initiative count 0. It takes 2 squares of movement to enter a square with crowds. The crowds provide cover for anyone who does so, enabling a Hide check and providing a bonus to Armor Class and on Reflex saves.
Directing Crowds

It takes a DC 15 Diplomacy check or DC 20 Intimidate check to convince a crowd to move in a particular direction, and the crowd must be able to hear or see the character making the attempt. It takes a full-round action to make the Diplomacy check, but only a free action to make the Intimidate check.

If two or more characters are trying to direct a crowd in different directions, they make opposed Diplomacy or Intimidate checks to determine whom the crowd listens to. The crowd ignores everyone if none of the characters’ check results beat the DCs given above.
Before I implied that it would take a complex skill check to control a mob. I'll leave the DC, but require 2 out of 3 successes, and give a -2 penalty for failing a roll. You can retry the check, but the penalties will still apply. This will apply to crowds and mobs alike. Now for mobs. If you have Lesser Lead Mob, it only takes a standard action to make the diplomacy check. I'll make the intimidate check a standard action, too. It's a lot easier to intimidate a mob than most people think. When the mob has a leader (not necessarily one with levels in Mob Leader), the leader can oppose an intimidate check with a diplomacy check, but must give up his next standard action. The person intimidating has to win by five (the difference between the checks), and get at least 15. If one of the people in the mob is killed, whoever killed him can make the intimidate check as a free action, with a +5 circumstance bonus. If he kills more than one person at once, each additional person adds +2. If he chucks a fireball into the center of the mob, don't bother with the check; the mob disperses. The leader can oppose the check as before, and still takes the next standard action to do so. If the leader is killed, the mob disperses. If the leader is somehow incapacitated, and the mob knows he's not dead, it doesn't count.

In a crowd, you can move through it. In a mob, if they don't want you to move, you can't. Casting spells with somatic components is also impossible.

Any ideas on how damage is dealt, and how to tell when you kill a member in more than one hit?

Is that good enough? Is there a better way to write this?