It won't happen often, no. But the fact that no mitigation works against it, is stupid. If I play for example a warrior and defstance and shieldwall are active, I will survive an execute with 10% hp. Or let's add pain sup on top of that. The warrior would survive an execute or another high dmg finisher. But the monk's touch would kill him. I remember a lot of close fights from the past, were I or my mates survived thanks to damn close calls.
And this video also showed that once the ability is used, the target will die. The spell didn't make a distinction between the warlocks and warriors health.
All I am saying is, that this ability might cause quite some turmoil in the future because it simply kills and is impossible to avoid unless you manage to stay above 10% hp for the whole time.