4 mana destroy a minion is pretty average for the effect. Doesn't silence. Never ever use before turn 10.
I'm not sure it's a mainstay in Reno Lock.,. if you've made it to turn 10 you're probably not too worried about spending 4 mana to kill a single minion.
It also doesn't help you against your biggest weakness, aggro.. cuz you're pretty screwed if you use it on turn 4. Between the new AOEs, the new minion, and the possible new legendary I'm not sure you have room for this. Maybe. Let's not underestimate how crippling losing a mana crystal is for RenoLock against any aggro/mid deck, it's desperation mode.
Early game, it might handicap you badly enough you might lose easily. On the other hand, in the late-game, it's essentially better than Assassinate. Assassinate being good in arena, this might be pretty good as well. I can't be sure, obviously, but it seems a fair chance.
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So, when a warrior uses Dead Man's Hand, what does that actually mean in terms of flavor? Is he the dead man? Does he cut off his own hand? Is that why he has Tentacles for Arms? Does he think that tentacles are actually as good as arms?
These reasons and more are why I think warriors are more mysterious than people give them credit for.
You could play this on turn 8 and it would be the same mana spent overall as Siphon Soul, without the healing. (4 mana cost and an extra "Overload: 1" for the next 2 turns.) It's not bad for a desperate situation that requires the 2 mana RIGHT NOW compared to Siphon Soul. Of course at 10 mana the drawback is irrelevant.
For the arena, though, this is a common viable removal spell for warlocks. This means warlocks can now deal with big threats more frequently instead of relying solely upon rare cards (primarily Siphon Soul, sometimes Doomguard, very rarely Void Crusher) to target 5+ health minions. The drawback isn't so bad since you wouldn't play this early, unless your 2- or 3-drop was worth it or the target is actually that threatening. Likely, this will be at it's best in the late game where you can remove a minion, Life Tap, and play a 4-drop.
Doesn't seem playable, the drawback is devestating before T10 and if you've made it that far with Renolock then you're already doing well. There's also just little chance BGH wouldn't be better than this even after the nerf.