Overrun is a great maneuver. My favorite in fact, because it causes the least problems for a GM. Grab, Trip, Dirty Trick, & Disarm mess up the target and makes the GM divert from tactics. Bullrush and Reposition move the guy around and aren't as bad, but still annoying. But Overrun? You get behind the person and maybe do some damage. That could be significant damage with the right build, but it's just damage.
I agree with Big Norse Wolf though. When you charge, you can either stop and hit the guy or Overrun him, not both. Unless you get Charge Through, in which case you can charge Target A, Overrun Target B on the way, then hit Target A when you get there. Note that this still doesn't let you overrun and swing at the same target from behind - Charge Through has to be a second target as it doesn't overrule Charge's requirement of 'must move to the closest square from which you can attack the opponent'
The Overrunner goes on missions for the society. Sometimes a dwarven milkman happens to show up in town and do a bit of business while the party is gathering information.
The Overrunner uses Bulette Style. But is not a deer. The Overrunner is very multi-class, so much of this will not help you, but maybe you learn something.
Relevant to a single class shifter though...
Traits: Favored Champion and Giant-harried
Feats not shown above:
Tribal Scars (Greattusk): 6 HP, +2 to Overrun, and +2 to ride.
Hard Headed: +1 CMB if you've got a specific helmet.
About Bulette Style. Bulette Leap is the real winner here. Basically you can play checkers across the map every turn, for the cost of -2 on each piece you leap over until you fail. And with your build to do damage to each one, it gets nifty.
Gear:
Dwarven Boulder Helmet (if Hard Headed)
Titanic Armor: Count as a size bigger for CMB, which determines what you can Overrun. But as it's a +3 bonus, stacking it onto Wild armor is hugely expensive. Honestly since Wild got nerfed, and you're looking at Stag as your main form, you might be better off just buying Stag Barding. And don't forget the armor spikes.
Tusk Blades: Put these on your horns to make your gore attack better.
Brawling enchantment: I'll leave you to find a way to get a weapon you can put this on, but you add its enhancement bonus on CMB.
Belt of Thunderous Charging: +2str belt, adds another +2 to bull rush and overrun. And your weapons count as a size bigger when you charge.
Boots of the Mastodon: +2 enhancement to overrun and some activated abilities.
Demonspike Pauldrons: Your armor spikes do more damage (for use with Spiked Destroyer)
Gauntlet of the Skilled Maneuver: +2 Overrun.
Gladiator's sandals: If you do a cmb in a surprise round, you get +4. Situational though, and might count as Activation.
Dusty Rose Prism Ioun Stone: Not as good as it used to be, but put it in a Wayfinder and get +1 to CMB.
Silvery Thorny Ioun Stone: +2 to Overrun (competence)
Victor's Belt: +2 to CMB, but generally not as good as the other belt.
Potion of Aspect of the Bear: +2 AC and CMB while it lasts. Doesn't stack with Boots of the Mastodon.
The Overrunner:
Race: Dwarf, adopted by Shoanti, follows Gorum
Traits: Favored Champion (1/d: Reroll a combat maneuver check)
Giant-harried (+1 on CMB & CMD vs things bigger than me)
Fighter stacks Foehammer and Siegebreaker. Breaker rush does damage to things I overrun, Breaker Momentum gives me a free overrun after I bull rush, Sledgehammer gives me +2 to overrun.
Barbarian is Armored Hulk. Overbearing Advance adds my strength as damage to things I overrun.
Vigilante is Avenger version. Favored Maneuver gives me Improved Overrun and a +2 if they're unaware of me. If I take more levels I can get Nothing Can Stop Me to get rid of something between me and the target.
A level of Oracle (Apocalypse) gives me Unstoppable Overrun, so I can go through things 2 sizes bigger than me.
Since I'll be getting into flank anyways, 2 levels of Rogue lets me tag Slow Reactions or Distracting Attack onto a sneak attack, so the target either can't take AoO's or is flat footed, respectively.
