Okay, so I've been mulling about this mechanic (Overrun), and I believe I have it down to some extent, but I'd like clarification. This is how I am aware the manoever works:
An Overrun is a combat maneuver and uses your CMB plus modifiers from improved manoever feats against the targets CMD, in an effort to continue a move action after colliding with a target. This prompts an attack of opportunity if the character does not have the improved overrun feat.
You may only have one target per overrun attempt.
The target of an overrun must be one size category larger than the character or smaller.
An Overrun may be made as a standard action during either A) at the end of (or during) a move action as an ordinary standard action, or B) as part of a charge (double move in a straight line) replacing the attack with a combat manoever attempt yielding the same +2 bonus, and -2 to AC as an irregular standard action that replaces your intended attack.
If the character declaring an overrun is not trained (doesn't have the improved overrun feat), the target of an overrun has a choice of whether he or she attempts to block the overrun, OR allow the overrunning character to continue past without opposition (with the improved overrun feat, the target must attempt to block the overrun)
An Overrun used as part of a charge can be used unintended in two different ways: A character charging into an enemy may have a creature blocking the path, if this character declares the charge attack on the enemy, the unintended overrun target (the creature in the path) can attempt to resist the charge becoming an unintended overrun target. If the creature is able to choose to get out of the way, he may do so, and therefore leaving the charge attack still open against the enemy. The second way is that instead of a creature already in the way, there is a trigger set to place an enemy in the path of a charge, in which case this unintended target is treated just as the last example.
If an overrun is blocked, whether by choice or not, you roll 1D20 and add your CMB plus overrun modifiers. If it beats the targets CMD, the overrun is a success, and you may continue your move action or charge as normal. If the overrun fails to beat the targets CMD, you stop one square before you would have reached the target, and you have used both your actions in the turn, ending your turn. In addition to a success, if you exceed the targets CMD by at least five, the overrun also makes the target prone in its original square.
If I am correct in my assumptions, I have a few questions. If not, then ignore what I'm about to ask, as its based off these prior statements.
What is the value of forcing a target to block an overrun, in terms of an intended charge attack? Isn't it more advantageous to have the target choose to get out of the way, leaving you with the ability to make the charge attack you intended? The only benefit I see to forcing an enemy to take the overrun is if you intend on making the enemy prone, and then having an additional movement, but thats very niche in practice, and has a +5 adjustment to the DC making it also quite difficult.
Since there can only be one target per overrun attempt, doesn't that put larger size category creatures at a massive disadvantage? Larger creatures occupy more spaces, so there is more room for enemies to get in the way, meaning that if there is a line of small/medium sized enemies horizontally, a medium overrun specialist is more able to continue his move than a large or huge creature, as medium creatures can pick one target, and move through them, and Large creatures can overrun one enemy, and then forced to stop by an adjacent enemy. This doesnt seem to make sense mechanically, or logically.
If the purpose of an overrun is to move through a divide, why are there so many obstacles to doing so? If there is one large enemy (10ft x 10ft), a medium character can push past it reasonably, but if there are two medium creatures (10ft x 5ft) both in the path of an overrun, then it becomes an infeasible task for the same medium sized character.
(bonus question) In my search for answers, it seems that some DM's have treated overrun as if it has always has the feat "charge through" for the purposes of fixing the underperforming manoever, but I feel that this is excessive, and doesn't fix the real issue of allowing characters to move through enemies more consistently, as that seems to be the more express purpose of the manoever. Does anyone else find this simultaneously too overpowered of a fix, and too unfocused, or is that just me?
I really like the idea of overrunning and I want to make an animal companion that specializes in this for my Mammoth Rider prestige class character, but it doesn't seem like a mechanically effective ability in the first place, let alone for a huge creature.
Am I wrong in my understanding of the mechanic, or is it in fact this broken and useless?
I look forward to some answers. I can't seem to find answers anywhere else on the internet.