I'm sad to say that this is false. It's a Tool Tip error or the Weapon Skill is glitched.
Unbuffed C&S deals a single, 1-hit 100 potency attack. It is easy to test on a target dummy. Try it out:
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It is possible there is a mechanical error of the WS itself instead of being a translation error in the Tool Tip. Some numbers of note:
C&S gives the same amount of MP as a single combo'd Syphon (not a similar amount, identical). 884.
( 2 Syphons ) or ( 1 Syphon and 1 unbuffed C&S ) amount to the exact MP cost of Dark Arts. At 60, Syphon/C&S return 884 MP. Dark Arts cost us 1768 MP.
What's 884 * 2 ?
Blood Weapon returns 238 MP for every physical attack delivered. This includes Auto Attacks.
C&S - while under Blood Weapon - returns a single 238 MP from Blood Weapon, not three.
If there is an error in the Weapon Skill itself, and Carve & Split is suppose to register as three separate attacks, then:
Blood Weapon should be granting 238 MP three times, the Damage inflicted via C&S should be 3 times higher than Unleashed, and C&S's MP return should be equal to 3 Syphons, not just 1.
I hope it's a glitch, because if so, that means unbuffed C&S should reward 2652 MP instead of just 884. ( 884 * 3 )
The if/or situation of C&S -- choosing between a Dark Arts buff granting 450 potency, or vanilla 100 potency & a single Syphon's worth of MP -- is laughable. You're sacrificing 350 potency for the semi-equivalent of 1 stack of Wrath/Abandon. A complete joke. 350 potency is practically a DA buffed Souleater, and you've passed on that potency opportunity to regain only half of it's cost.
Now, if a vanilla Carve and Split granted 2652 MP instead of 884, that changes the situation. Players are given the choice of buffing C&S to use as a Damage WS, OR instead they can leave it vanilla and use it as a pseudo Infuriate with a 60 second recast.
Oh yea, Infuriate has a 60 second cool down too.
Quite a coincidence, it's possible the Weapon Skill is glitched.
Note: if it is glitched, I doubt a fix will increase the Dark Arts buff potency over 450. If it's three attacks at 450 potency each then that is a shocking 1350 potency overall.
More likely that C&S will have three attacks amounting to 100 potency overall (33 each), and when enhanced with Dark Arts each attack is increased to 150 potency (450 overall).
(While talking MP cost, how expensive is Dark Passenger? A: 884 MP. Dark Passenger is equal to one Syphon or Unbuffed C&S)