it's useless. Unless you're a zerker using it on a burn (2%) of 300k/s is still like a 6k heal per second or 36k HOT in comparison the shaman HOT is 6k. So for extra healing on your burn to survive AEs/rampage it helps especially on dead hills 1.
Assuming this is a proc, you can only proc ONCE per combat round, regardless of weapon procs, buffs etc, is my understanding. Not accounting for a twin proc, so basically useless yah.