Dark Arts needs some changes
MP in general on a DRK needs changes to be completely honest.
They nerfed blood price with too heavy of a hand, requiring you to take 20 hits to even get enough MP to pop a Dark Arts is insanity even if you include the blood generation Blood Price is now used for.
You never want to use Dark Arts on quietus unless all of these conditions are met:
Not in Grit
Bloodweapon is active
Number of Targets x 5 = more than the % mp you're currently missing
Dark Passenger is on cooldown
DP is 100 potency for 2400 where as spending it on quietus is only 50 for 2400 in the same ogcd slot.
Dark Passenger is straight bad in all situations excluding as an MP dump mentioned in the 1 situation above. The blind is less than a 5% miss chance on lvl 70 Ex roulette trash mobs. Not worth 50.6% of an MP bar.
The tank damage nerf has made abyssal self heals really really subpar and almost not worth the MP expenditure unless you're in one of those rare super-gigantic packs. This combined with the fact that souleater and abyssal only return 88% of damage dealt as HP @ lvl 70 now also nerfs it further.
TBN is fine as is outside of some stupid shenanigans involving having hit TBN before the wind up for some attacks even starts but the attacks ignore TBN completely, then TBN falls off. Maybe it needs a duration boost which wouldn't affect it's power much just make it less punishing for whiffing one.
Using DA on Dark Mind is only really useful now for incredibly niche 5s+ multiple strike magical tank busters. The cleave+buster combo in A12S and the shared buster in the final trial of SB are the only ones that come to mind.
Powerslash got changed somewhat if the testing threads are to be believed. Instead of increasing the multiplier by +1 from 5.5x to 6.5x (before grit) to adding double the enmity potency in a way similar to flash. I kind of like this.
Old Powerslash: 300 x 5.5 x = 1650 potency's worth of enmity
Old DA Powerslash: 300 x 6.5 = 1950 (+300 enmity for 2400 was bad)
New Powerslash: 300 x 5.5 = 1650 (unchanged)
New DA Powerslash: (300 x 5.5) + (300 x 5.5 damageless enmity boost) = 3300 enmity.
We need some interesting ways to spend our MP instead of mindlessly pressing the Dark Arts button every time we have the MP for it and don't need a TBN going up (Single Target) or just continuing to spam abyssals if we don't need TBN (aoe).
My personal thoughts (Keep in mind these are personal ramblings detached from the points I make above about their objective usefulness):
Give a 10% (20%?) Blind to DA quietus.
Un-nerf DP's MP cost or it's damage. Even just 1 of these would be fine.
Remove the Dark Arts bonus damage to dark passenger and change the blind effect into purging our own Living Dead from us. Preferrably in tandem with the MP being un-nerfed. Would still be worth the 50% of our mp bar in those situations where you can't get healed out of LD and it would useful in solo content. Extremely pricey MP wise, but this would be a dire situation warranting it.
Keep the Powerslash change, I can see the worth of effectively doubling the enmity multiplier to 11x over adding +1 to 5.5x.
Bump blood price to at least 10 strikes giving back a dark arts instead of 20.
Unmend -> Unleash interaction is functionally useless. Never have I ever said "Wow I'm glad that proc'd." Maybe this is just me. Maybe remove this and give hardslash a chance to make unmend go off the global.