Decay states "For 6 turns, when a champion would receive healing, it loses the same amount of health instead." but in practice (with a life siphon dude) I hit for 16, would heal for 8 but loss 4 life, not 8 as the spell says.
The ability was updated to be the current way a while ago, the description is bad. Soulreave works to counter decaying on life siphon champions btw.
Why the hell they changed the spell but didn't updated the text? It's harder the coding than the text change. Anyway, thanks for the info, and the advice too!
I posted about this a while back, but just to let you know we are aware of this issue. It is on our list to fix.