So the class basically does what I set out to do, it’s combat capable, extremely durable, and has a lot of very flavourful but still useful abilities.
At first level I would predict people taking the combat feat on top of their normal feat, but it’s not absolutely necessary to get off the ground. A lot of toughness/weapon group focus starts would get used, but the class could also take deft maneuvers and tactical maneuvers to start handing out some very synergistic bonuses and utility.
Mid game I would predict builds that make use of the soldiers tower shield talents and cover talents for some really good durability, or charisma based leadership characters. Later on a couple talents make the shock trooper abilities very useful, allowing a high save DC thunderstone/charge attack that is very much designed to immitate modern tactics. I often feel that magic fills the social role of technology in fantasy worlds, and tactics would naturally evolve to make use of it.
Hopefully by 7th level or so players would be able to pick a couple for-flavour talents, and then more as they approach 20. There are a lot of obviously powerful abilities, but the out of combat utility of someone that can maintain watch while sleeping or sleep throughout the day in cat naps is very handy for the usual camp outs that adventuring requires. The soldier class also includes a lot of built in ways to improve his saves vs a number of magical effects, making them far less vulnerable against casters than the old fighter class. One example of such a build would be to take evasion, shake it off, iron will, battlefield clarity, and then whatever other defensive and offensive abilities you might like. The result would be a character that is very hard to take out with just a single saving throw.
As a simple damage dealing entity, the soldier falls behind the basic fighter a bit. While a fighter gains 21 combat feats, a soldier gains 15 feats in the same vein. They can get improved initiative, toughness, weapon focus and greater weapon focus, and a bonus combat feat through talents and bonus feats. The rest of their bonus feats are purely teamwork, durability or mobility based. As a tank though, a soldier is far better than a fighter, able to make use of an enormous suite of talents and feats to keep themselves standing in the late game where fighters are just sidelined completely. With the same equipment a fighter gets, a soldier holds up exceedingly well.
Some sneaky improvements over the fighter class is the inclusion of Use Magic Device as a class skill. This was added in specifically as a late game skill. The biggest fall off of fighters is lack of ability to interact with magic.This gives a soldier at least a chance of picking up a wand and getting it to go off. I justify it to myself as the necessity of battle. Soldiers need to use every bit of leverage they can get their hands on, learn every trick. A soldier can pick up a wand of cure light wounds and save his buddies life if he can just get it to work. Really though, mechanically, the ability is just simply necessary, and doesn’t need much explaining. Rogues have the same ability and it still doesn’t push them into the realm of usefulness of a tier four class.