There are some good reviews of the SD tree. Most of those comments are dead-on so won't rehash them here. Overall I think the tree is a little bit better than what is on live. What is missing here (and I assume in DoS as well) is a reason to use a tank.
When we make a tank build we are by definition trading some DPS for survivability. That is fine as long as our personal lower DPS increases the party DPS or makes an encounter safer/easier for the party. Right now there are not enough encounters where a high defense character is a strong choice. I don't want it to be 'tank mandatory', but it should be a good and desirable option all the time.
I would like to see a boost to stalwart stance that boosts the party DPS in a noticable but not overpowering way.
Something along the lines of -10/20/30% fortification & spell damage boost on mobs that are agro'd on you as a debuff that lands with every successful intimidate or some such. This would be logical (mob is focused on the tank making its defense vs. others weaker) & make having a tank join the party viable and beneficial in more content than they are today.
This also gets to a weakness of defensive oriented trees. More defense is not always useful. Being 'more' of a kensai is almost always useful. You do more damage and things die faster. Being 'more' of a tank is not always that useful, but boosting the party is always good.