While a certain amount of RNG is fun in the game, I think this would be too random to be fun. Imagine how frustrating it would be if it chewed up 50-70% of your life just on bad luck. It would also render the Blood Demon completely unusable. No one wants to push their health down to 1% if they can end up killing themselves right after. A Battlecry for it that had a 50/50 chance of affecting health postively or negatively 10% would be more balanaced, but less fun I guess. I think in general though, for balance, Andy is a little leery of allowing too much manipulation of Health, because it can skew the balancing REALLY far each way. That said, my own personal guess is we will see more Health manipulation when the light deck comes out.
Well, i wonder if he meant the life of the wizard or the creeps life... There are many TDs out on warcraft 3, which have a tower to reduce creeps like (dont work on boss[challange])