i can hopefully provide some insight. a while ago, a shaman in our guild reported he seemed to be healing himself for a lot. so i went to check him out, sure enough, LHW on him were 1.5k more than me when we were completely unbuffed just standing around. he used Lifeblood and it healed him for something like 520 a tick, when it's not affected by spell power or anything so it had to be a bug. unfortunely, something has happened to get rid of it. he said it was happening for about week before it was fixed.
tl;dr- seen this sort of thing before, seemed to be a bug, was fixed after a week.