Defensive Combat Stance: While using Combat Expertise mode, you suffer -5 to your attack rolls but gain +10% feat bonus to Armor Class.
Spells have three times their normal cooldown when this mode is active.
Combat Expertise dispels and wards against all Rage effects.
(Note: The in-game description incorrectly implies that the to-hit and AC modifiers are limited by your Base Attack Bonus, and the AC bonus type is unspecified.)
Notes
Spell like abilities are not subjected to the increased cooldown
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In particular the three times their normal cooldown, especially since SLA abilities and ED abilities are not effected by this.
This was initially added as a replacement of dropping out of stance when a spell was cast. The idea was to prevent CE from being too good a feat that casters would use it to have a strong AC (not getting into the effectiveness of AC alone in this discussion). With the loss of stance and now with 3x cooldown by far the melee caster be it divine or arcane is effected the most by this.
I want to propose a different penalty instead that helps prevent this from being too good with spell casters but does not pose such a penalty on the Melee character that happens to use spells also. Reduce the cooldown of 3x to 1.5x and reduce the DC of spells by 2 and reduce Spell Penetration by 1; thematically because your concentration is on your defense so it is harder to keep your concentration on the resistance of your spell.
The cooldown still is a trade off for the melee type that uses only healing/buffs but also makes this a trade off for the primary caster that is looking to CE for more defense.
Just a thought is all.