You can always cast<em>Magic Fang</em>on your Animal Companion, and let it do the DR piercing.  And even though you said you were going to concentrate on healing, I<strong>strongly</strong>recommend Augment Summoning; the ability to get a battalion of beasts with +4 Str and Con is no small one, especially in a game like this.  Since you can't spontatneously heal like a cleric can, you'll probably want to buy a wand of Cure Light Wounds or two.