This is the second card in the "exactly" cycle after Stealth Training. It's not quite as useful as that. Stuns are obviously more valuable than removing a bit of threat. But just because this compares poorly to that doesn't mean it's bad.
Removing threat is usually worth the ER paid to do so. So removing 2 threat is worth 2-ER. Since this is worth 2-ER, it's paid for itself after you defeat a minion with 2 threat, or two minions with 1. This is a card that should pay for itself pretty quickly, and start netting positive value after a few turns if you're able to trigger it consistently. Unfortunately, some minions will have no scheme, making this useless against them. This does need built around a bit more, but allies can be good for pinging enemies to wear them down enough for you to get the finishing blow.
One tradeoff is that the "exactly" archetype has some anti-synergy with the overkill archetype. Moment of Triumph, Into the Fray and No Quarter are not going to do well in a deck using this. This also doesn't work well with strategies based on increasing your ATK.
Another thing this synergizes with is cards like Warrior Skill which can increase the damage of any attack by 1 when you need it.
What this archetype is really intended for though is Martial Artists. This is why Stick can decrease your basic attack in addition to increasing it. This gives martial artists a decent range. And if the finishing blow is a basic attack, then it also synergizes well with cards like Blood Rage.
While a fine card on its own though, I'm not sure if I'd want to build around it today. It's not a bad card. But I feel other minion killing archetypes just have better payoffs.
That is what I'm saying today, anyway. After Elektra comes out with additional support for martial artists to benefit from exactly defeating enemies, I might revisit this.