I like the idea of TBN activating a Bloodspiller proc that increases its potency. One problem with these recent patch changes is that every time you boost the value of DRK's combo potency relative to Bloodspiller, you change it from a dps gain to a dps loss. So we've flip-flopped from a 19 potency loss, to a 4 potency gain, back to a 3 potency loss over three consecutive sub-patches.If TBN breaking applied, say, a built in DA effect to the next Bloodspiller, then it would be a consistent dps gain, regardless of how the devs tweaked the potencies. It would also make it feel more like a counterattack.
I think the single biggest issue with DRK at the moment are the stance penalties. BW is functionally similar to FoF or Berserk, but is only accessible outside of Grit and is terminated by switching stances. Delirium is strong, but also commits you to spending the next 23-30 seconds locked in whatever stance you started out in, and any stance swaps that occur during this period completely waste the effect (costing you over 200 potency). Blood Price looks like it's tuned for having multiple targets present, but you need to be hit about 3-4 times per second for it to be comparable to BW (in practice, this happens in situations where you have about 9+ mobs attacking you). The passive blood gain somewhat helps, but there at least needs to be a passive MP gain if it's going to be tuned so low. Overall, in order to make full use of these cooldowns, you need significantly more planning than you would for either FoF or Berserk, and mistakes are punished much more harshly. That's not even including the issue of the MP penalty associated with stance swaps.
I will say that I like what they did with Quietus. There's a neat interaction with TBN there that makes AoE tanking really fun. Unfortunately, this makes BP even less desirable, as there's little reason to use Delirium on it.