Well it relies heavily on your charisma - since you can only "avoid" a number of creatures equal to your charisma modifier. So it not only provides a feat tax, but also a degree of MAD to the cleric.
Compare the ability to casting a spell instead. Or attacking in combat under the effects of several Personal buffs. 3D6 damage isn't that great when wizards at the same level are tossing out fireballs that deal 5D6 (and direct damage isn't even considered a wizard's best ability either).