Shield Brace would be a better choice insead of Phalanx Soldier.
As you are Two-Weapon Fighting an Unchained Barbarian is more benificial due to how bonus' are added.
Honestly, for the phalanx-look, you're probably better off playing a pure phalanx soldier fighter. Or a pure barbarian with shield and shortspear. I've build both for fun just a few days ago (though my barb swings an axe). And either one is a pretty good character.
If you do go for Phalanx 3/Barbarian 7+, however, here are some pointers.
- Do something about your low will save. Yes, it's important, so it's bold. Be a dwarf with Steel Soul or maybe a Half-Elf with the Dual-Minded alternate racial trait. Consider Birthmark as trait and the feat Iron Will in either case.
- If you use a reach wepaon, get Improved Shield Bash so you can hit and threaten foes adjacent to you when 5-foot-steps are not possible.
- Ignore Two-Weapon Fighting. It costs too many feats for too little gain on that kind of character.
- Pick the Invulnerable Rager archetype.
- Assuming you care for defense more than offense: Be an Unchained Barbarian. Get Beast Totem (and its lesser version purely as pre-requisite) and Guarded Stance for a decent boost to your AC while raging. You can also get Pounce via Greater Beast Totem later, which is probably the best ability any melee character can have.
- From barbarian level 8 onward, get the Increase Dmage Reduction ragepower. With Extra Rage Power you could have DR 8/- in rage at level 11.