I'm sure I wasn't the only one who misunderstood the talent when I first read it, so let me ask what may be a stupid question:
You do realize that it resets the remaining time of an existing Divine Plea buff to 15 seconds, not the CD of the spell, right? You punch it once and as long as you keep hitting things it never drops off.
If the buff is really dropping, then either you have the talent display bug that people started encountering after 3.1 - where it shows you as having talents that you do not, or you have encountered a legitimate bug. Ticket a GM for the former, post in the bug report forum for the latter.