Woot! First character submission.
Not familiar with Dragon Disciple, but now that I'm checking the description I'm thinking we may have a "no prestige classes" rule. The character bio itself is fine, but forgive me if I have a difficult time reconciling your statement that you were going to avoid powergaming and yet you want a class that the NWN wiki claims is basically one of the most powerful classes in the game with a massive pile of super abilities, several immunities and a +14 attribute points bonus at level 10.
...yeah. I'm going to rule base classes only:
* Barbarian
* Bard
* Cleric
* Druid
* Fighter
* Monk
* Paladin
* Ranger
* Rogue
* Sorcerer
* Wizard
What about other prestige classes, like Dwarven Defender, Champion of Torm, Shadowdancer, Shifter and such. While I personally find RDD a rather meh class with its only saving grace being the huge +14 attribute points, some of the other prestige classes in nwn have nowhere near the bonuses RDD gains.
Shadowdancer's first lvl feat "Hide in Plain Sight" is indeed OP, but the rest of the class is fairly nice. And I like it for the rogue like abilities it grants on the side for chars that didn't multi into a normal rogue. That HIPS feat alone is what makes the SD class OP in my opinion. Though a simple true seeing spell/ability, nukes the feats usefulness.
Palemaster can be OP with the 10th lvl crit/sneak attack immunity, and gobs of extra ac. Honestly I consider PM to be far more OP than RDD. Especially on a melee build. PM actually sorta handicaps a caster build the more you take of it. The extra abilities it gives beyond lvl 10 aren't worth the caster lvls you would lose for it.
RDD, you've already covered has a large amount of the red dragon super ablities and the huge stat bonuses. And any caster attempting to take rdd is going to gimp themselves in the long run anyways. The OP'ness of this class comes from a melee char abusing it, much like they would abuse a PM.
Those are probably the 3 most overpowered of the prestige classes off the top of my head. And do make for strong chars jus simply based on them alone, but like most every class in nwn its how you combine them with the base classes that makes them really shine into the potential behemoths that they can be.
Anyways I can still make a char without them, but jus putting out an arguement for some of the other prestige classes that are actually balanced.
I have done my fair share of power gaming on nwn, and I still know a significant amount of ways to put together some absurd characters. I can give you a fairly good run-down of most any class you want, here or in a pm if you don't want that knowledge out there.