What has DR/piercing other than spearblock armor? Besides, the heavy mace is a solid choice, cause the worse crit is one less damage roll, and that's if you succeed on the threat roll.
Raksasha comes to mind, though its kinda moot if you aren't also using a holy weapon.

As the frost spell from PHB2 grants dr magic piercing.

Though as a warblade, you do have a few ways of overcoming dr, from mountain hammer to shards of granite.