A couple of nuts & bolts regarding a matchup between a normal Fighter and a Weapons Master

Things to bear in mind

Sunder

Any combatant may attempt to break another combatant’s weapon or shield as a standard action. It comes at the price of an attack of opportunity. When at level 12 a Weapon Master and a Fighter that are otherwise equal lock horns, I would recommend that the Fighter use his Sunder ability and improved initiative to break his foe’s weapon.

In the case of a Warhammer, the target weapon has a hardness of 5 and 5 hit points (on its haft, which is wooden). This means that the first 5 points of damage are absorbed from any blow, and when 5 hit points of damage get through, the weapon will be rendered unusable. The two sample characters do 1d8 + 1 (masterwork) + 2 (weapon specialization) + 4 (strength) damage without even using the power attack feat that both have. On average, any given successful hit will do 10.5 damage, enough to break his opponent’s weapon with one shot.

To attack an opponent’s weapon, you make an opposed attack roll. The Weapon Master has a slightly better attack bonus, courtesy of Superior Weapon Focus.

For the Fighter to hit his opponent’s weapon, he’ll have to roll 1 better on a d20. There is a 45% chance that this will happen, and then good odds that the weapon will be broken. The Fighter is likely to go first, due to his Improved Initiative, so this is a good chance to force his opponent to resort to a secondary weapon.

Presuming that his weapon isn’t broken, the Weapon Master needs to roll no more than 1 worse than his opponent on a d20. There is a 55% chance of this happening. Upon landing the blow, the Weapon Master may use his Ki Damage ability to ensure maximum damage (14), which is more than enough to break the Fighter’s weapon. He may use this ability 6 times per day, so this may be a good time to take advantage of it. When the Weapon Master attempts to attack the Fighter’s weapon, he provokes an attack of opportunity.