Lammanian testers misinformed us:

[Junts]

The holy burst on a crafted ring will stack, at the very least, with holy handwraps: using holy handwraps with such a ring creates two separate 2d6 good damage rolls per non-critical hit.

It does not stack with another holy burst effect, but using holy handwraps with a ring will get you 4d6 holy per hit.

[NXPlasmid]

Woot!