The way this works is that when the proc happens (which is a 10% chance whenever a hot or direct spell heals, with a 45 sec internal cooldown) you gain a buff (the Blessing) on yourself. Now all of your heals for the next 15 sec cause an 8 sec damage shield. The shield stacks with itself. It includes healing done by subsequent ticks of existing hots on the target. Note that the spell has to actually heal, so hots ticking on a fully-healed target cannot cause the proc. However the shield is based on the size of the heal itself, not the amount healed â€“ i.e. 100% overhealing will not proc the Blessing on the healer, but the shield itself includes overhealing once the Blessing is active. The shield can grow to a maximum size of 20,000 damage absorbed.
With that said, I'm curious how people feel about the proc. Is it truly equally effective for all healing classes? Are all classes capable of a 20k bubble? Are there any especially creative uses for the 20k shield in the current pve content? What class do people plan to give the mace to and why? What are the pvp implications?
edit: Updated after Ralnar's post below, thanks.