The bonus AB from this perk does not stack with bless, divine favor, or a few other similar effects that are quite common on clerics.
Some stacking issues previously reported. (//%22http://www.escapefromundeath.com/forums/showthread.php?t=45419%22)
This exact bug thread + discussion. (//%22http://www.escapefromundeath.com/forums/showthread.php?t=51309%22)