There are several problems with combat expertise from a Dwarven Defender perspective.
1) You need to have a 13 intelligence to get Combat expertise. If you are using point buy or the standard array, you are not going to have a 13 intelligence. As a Dwarven Defender, your stat priorities are Str, Con, and Dex. Dex has to be at least a 13 to get Dodge. Str for offense, if you don't have a tough offense, all the defense in the world won't matter. Con for hit points and keeping your stance going longer. Wisdom is good because, as a fighter type, you can expect all sorts of mind control/charm/hold type spells. Which means Intelligence is either going to be your 5th or 6th characteristic. If you multiclass to Paladin, then Charisma has to be high, and intelligence is dead last.
As an example, my 28 point buy Fighter/Paladin/Dwarven Defender had the following 1st level stats:
Str 14, Dex 14, Con 16, Chr 12, Wis 12, Int 8
2) If you don't have a high offense, all the defense in the world won't matter because the enemies will ignore you. So, I really dislike taking a -5 to hit, especially since the -5 to hit will also apply to your AOO's and your AOO's are very important against grapple attempts. Expect a lot of Giants, Trolls, Bears and so on to try and grapple you.
3) If you really want a tough defense, bring along a tower shield. Then use the tower shield when you need to make yourself even harder to hit.
DeathOfRats said:
Also, why is combat expertise useless for a DD? I would have thought in situations that required it you would be able to get an insane AC bonus from all factors, +4 DD bonus, +4 defensive stance bonus, +5 combat expertise bonus, say +5 from a +3 shield, +11 from a +3 full plate, +3 from a +3 RoP, and +3 from an amulet of nat. armor brings you to 45 AC.