So what benefit does the spear have over 2-handed sword?
The 2H Sword has 1.5m range vs 2.5m range on the Spear. Considering this, the damage trade-off seems fair, until you realize Bows have much more range than the Spear and still more damage.
There also tend to be more 2H Str weapons, so those using them will get more-frequent upgrades as drops.
Comparing Bows to Spears, bows have >5x the range, ~2% more damage, the potential to benefit from high ground, and a plethora of elemental arrows.
Spears have Warfare Skills, but Bows have Hunstman Skills.
It makes Spears seem kinda bad, but since the available Skills are different the comparison isn't as straight-forward.
