I use blood reaper mostly on DPSlayer, but I also keep a single Firebrand Imp in my deck for emergency bloodreaperization. Because it is a level 1 spell, blood reaper only costs 2 Life, which means that it can heal off the damage in a single round. After that it is pure healing, which often makes my opponent try to kill the imp. That further decreases the amount of dice they are throwing on my Mage.

What do you mean by heal off the damage in a single round? Blood reaper doesn't give you damage, but takes away from your maximum life. You cant get that back by healing. Maybe that's what you meant though, just wanted to point it out anyway.