BALANCE:
The class features a collection of defensive abilities, most of which are replica from core classes. It seems to me that it is quite well balanced: compared for ex. with the Barbarian, it has AC bonus, Defensive Stance and better ST in place of Rage and more skills.
FEATURES:
The only unique ability is the Defensive Stance. While the benefits are definitely better than the Rage ones (less Str but a net +6 in AC), the fact you can't move is an excessive hindrance: it makes the ability useful only in some circumstances. If by default a 5ft step was allowed, it would have made much more sense, without overpowering the ability at all (it would still be a serious hindrance, but less ridiculous).
FLAVOR/RP:
The class is a very good idea: a dwarven warrior experienced in defence, possibly in defense of someone else or a place of importance. Given the traditional view of Dwarves as very resistant beings, difficult to move them from their "positions" (both in physical and metaphorical sense), the racial nature of this PrCl hits the point very well, and can be used by the DM to add more cultural distinction to the race by creating an elite of NPCs for example.
REQUIREMENTS:
Well thought, less well designed: with these requirements, every "beginner" Dwarven Defender is supposed to have already a good combat background (from BAB) and defensive/resistance abilities (the Feats), and that is very fine. But honestly, there is no real reason to require EXACTLY those feats: if they had been instead Dodge, Expertise and Iron Will, it would not have made any difference. I think the best solution could have been a list of 7-8 feats, among which the candidate should own at least 3 or 4. Instead, Endurance and Toughness look like they are just "costs" to qualify, which is generally a symptom of coward* design: requirements which are going to be never taken advantage of during the career in the PrCl reveal the writer's fear of making the PrCl too powerful.
On the other hand, it is good that no requirement implies the PC to be of a specific class.
*I apologize with the author that this expression sounds insulting: I don't want it to be... I just can't recall a better word in English
DESIGN:
The global design is very good: the writer collected the best defensive abilities around, changed some of them (AC bonus/DR with different progressions than Monk's/Barbarian's), except Reflex saves, which anyway makes perfect sense to be not the best.
A modest question: why duplicating Uncanny Dodge with a different name and then even clarify it stacks from the same ability of Barbarians and Rogues?
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OVERALL: 7