That would be a fun deck. I don't think it would be too overpowered though... It would deal the reduction twice though.
I guess it is an 8-card OTK right?
Voodoo doll + 3 BB + ability + 3*TU = 80 + 3 * 40 = 200 damage.
I guess that suggests it is close to balanced, but I think it would be the cheapest OTK quanta-wise.
I think it would be much more reliable than voodoo bravery since you don't have to mess around with gravity force.
8 card OTK is sufficiently difficult to pull off that it should be balanced if you cant reasonably play any pieces before hand.
I actually think this is really a "7 card OTK" since Voodoo dolls are fairly safe to play, so there is no need to hang on to one in hand until ready.
still 7 card combos are not that easy to set up so I dont think it will be a problem.
...
I know its a big change but what do you think about making it deal the damage to a random target?
That would be an implicit counter to SoFo abuse since SoFo could end up being that target, killing it instantly (first half hp lost by ability, then damage removes last half of HP).
Of course, then you have a potential auto-killer ... but you risk killing your own creatures at the same time... or hurting yourself really bad.
As a last note, the targeting would be random... but that doesn't mean it cant be a biased random... i.e. higher priority to enemies or high HP allies.
you could word it as:
"
: Target creature loses 50% HPs. Deal 1 damage per lost HP to a random victim."