Im not 100% sure what u mean
here. in the talent tree I suggest I have 2 (not 1) points in blackjack. The dmg from coup the grace has 2 (not 3) points.
Talent Calculator - World of Warcraft
IMO, blackjack is a game changer, but 1 talent in it is not worth it. I would rather lose the extra dmg on evis for the insanely nice blackjack. Remember, in a 1v1 you might sap somone and then cheap shoot them, but in arena you sap the offtarget and cheap shoot the main target. Alternativly sap main target, then offtarget, then cheap shoot main target so he gets a debuf for a few sek. But depending on the opponents you can also ambush the main target because if he now has the debuf hes not gonna do much damage any ways. Also, in BG, you can be the designated debuffer

Saping people all the time so whoel enemy team does shit dmg
I could go on, but main point is. Go for blackjack 2 points IMO. Remember blackjack gives the debuf even if its 3/4 dr on the target already. So even if its only a tiny sap, your 8 sek debuf stil works. And trust me, 70% less damage for 8 sek is insane!