Game Mechanics: Shaman Canna

[Sigleaf]

I just recently noticed that on my shaman when using cannabalize it commonly bugs out and instead of stealing 50 hp and rewarding 20ish mana, it commonly takes 50 hp and gives me 7-8 mana. I have to relog and sometimes that fixes it but other times it doesn't. No idea if this applies to the other cannabalizes but the first one is most certainly bugged.