I'm going to have a hell of a time stabbing a spartan using a shield and a boar spear with two weapon defense.
Just throwing it in here, that two hoplite style soldiers are devastating. Nearly not to scratch thanks to their armor and shield feats and rocking spear basics allowed them to elevate the humble throwing spear to a murderous implement of far reaching death. What's even worse was the Phalanx Fighting stance from Shield Basics turned them into REALLY hard to hit opponents. Up to +4 defense made a HUGE difference.
The Armor feats accounted for +2 DR and immunity to sneak attack damage, the Shield feats gave their metal shields a guard of +4 and Phalanx Fighting gave them up to +4 on Defense too if they stayed together and to top it all off their simple throwing spears ended up with a reach of +2. Add in the defense and DR bonuses a Soldier gets and it got ridiculous.
On the other hand their lack of feats like cleave or all-out attack for a long time took care that they excelled defensively but didn't kill enemies as fast as other warriors, but if someone needed guys to hold the line they were just damn perfect.
Polearm tree works just as well as the spear tree. The two trees work together pretty well.