First, forgive me that I will not use the per-argument format the way you do, hope you don't mind. (°u° )

Dark Passenger - updated version looks fine to me, you got a fair point regarding the enmity and in retrospect I can now see it as a Circle of Scorn with DRK flavour regarding MP cost and increased damage. Eventually comes down to the mathmaticians in our community to determine how much DPS it will give.

Dark Mind - While you have a fair point regarding uptime and DRK not having an anti-knockback ability unlike almost everyone else in the game, I personally think that the trend of 30s / 60s "cheese knockback mechanic" abilities is a bad thing for the future of fight designs. Knockback mechanics can now be entirely circumvented on demand, rather than having to actually do the mechanic properly. In my personal opinion I'd nerf said cooldowns to 90s+ to make the cooldown placement matter more. Back in the statement of knockback immunities I suggested reworking some role action skills to rotate out of the list and be swapped with other skills that are more situational but still good, giving you more of a choice. Simply put, Tempered Will in role actions.

Shadow Wall - Your statement about bad fluff mitigation is not without merit, but putting critical nullification on it isn't the right solvent. Against magic damage, DRK has decent fluff mitigation in form of Dark Mind and / or Rampart, where it lacks is physical fluff mitigation without TBN - which on its own is not great to mitigate fluff but rather busters. An idea would be to move the currently rock-bottom tiered role action "Anticipation", aka HW Dark Dance without evasion out of the role action and bring it back as "Dark Dance", although maybe with a 40% parry chance instead. On a further note this could allow to bring back the parry-punishment engine with Reprisal and Low Blow, although with different names and effects in a similar fashion of PLD's shield swipe. To make DRK not look completely dorky as an Off-Tank or in magic battles, you could chain TBN's shield break to count as a successful parry to activate the effects.

Alternatively, based on Yoshida's response about Shadow Wall's cooldown that fights are designed around cooldown timers of tanks, an additional 5 seconds of duration would instead be a fine solvent, although a relatively lackluster one.

Plunge - fair enough on that, indeed having to sit on a 200 potency ogcd rather than a 100 potency one is indeed frustrating.

Carve and Spit - Without taking Crit and DH buffs into consideration, the equalizing of chances is overall not too bad. However the benefit is not so great if you play in a party setup that boasts with crit and direct hit buffs (DRG, SCH, BRD, etc). Theoretically speaking, we have a 15% chance of Crit without buffs and about 40% with buffs (Battle Litany + Chain Strategem). If it was a single hit, it would be a 40% chance to crit and either is or isn't and be done with it. With a three-fold attack that calculates criticals individually, you have to go through each hit with a 40% chance. To get the same benefit as single hit CaS, all three need to crit, which in theory is a chance of 40%*0.4*0.4, which results in a chance as low as 6.4% to get the same output of hitting a single critical hit. Depending on the crit damage multiplier you have at that moment it could have devastating effects on criticals.

About the explanation of your Blood Gauge gain - while indeed it would end up the same MP cost of TBN, it lacks the possible penalty for such a high gauge gain compared to TBN. If using DA-CaS would have some sort of risk of not delivering blood given specific circumstances (like TBN with shield not breaking = loss) it would justify the 50 gauge on top of being one of the heaviest hitters, otherwise it would end up as a riskless Delirium setup (which gives back the 2400 mana already). So either a condition where gauge gain can fail or it should be lower, but 30-40 instead to not have as big as a gap as I suggested earlier.