Assuming lances have any real advantage over normal forms of melee. As far as I can see so far, they're just... different. How they compare in terms of one-hit potential, dps, and aoe mob clearing still isn't clear to me.
You can totally just rank the skills for the stats and stick to traditional forms of melee.
As for the defensive argument, yes, those spears were definitely used more defensively, but they were also built differently. And it's true as well that spears have been used on horseback.
But it's not like what things have actually been used for are really limiting factors in creativity... Unless people actually fought with ice cream swords at some point I'm unaware of.
Well those weapons are joke weapons. Can't really be compared to anything.
I gave an example where it WAS used defensive and offensively.
The strength of lances and spears (Brionac) are represented accurately in the fact that they deal damage past the defense and protection of an enemy (striking weakpoints) and aren't all weapons "different"
EDIT: MP only really makes a difference for those strictly concerned about cost. I am talking about the actual ability (power)