The Warring States
General Rule Changes for Feats
When a feat grants a bonus to AC, the bonus is reduced by 75% (minimum +1) and applied to Defensive Actions instead.
This means the Dodge Feat would reduce it’s bonus to +1/4, but still grant a +1 to dodge bonuses, but it instead applies to any attack, not a single opponent.
Also, the bonus from Combat Expertise would increase your Defensive Actions by +1 for every -1 to attack rolls.
Skill Based Feats are Unchanged.
The Combat actions for Tumble are handled differently. Tumble bonuses make you harder to hit overall for their purposes. When you are fighting defensively or using the full defense action as part of a tumble, you gain triple the modifiers to your base AC instead of reducing them by 3/4.