Actually, spell defense is very effective against divine magic; the auto- hit rule applies to hitting and casting dc, not spell defense. Which means low level divine spells suck against spell defense.
There are feats in Adventure Companion specifically to let divine casters grapple with this.
Since divine casters (at least, the Priest) don't have Spellcasting as a class skill, does this mean that any Spell Defense higher than 15 is an "you shall never touch me with your silly miracle" kind of defense ?