Blood Weapon / other DRK suggestions:

[Yuni_Queen]

In a single-target situation, as I just mentioned, your Mana is only used to DA a Souleater or to shoot off Dark Passenger and DA+CaS. If you're lacking for the latter two, you wasted too much on the former one. I say wasted, because DA+SE is the least efficient use of Mana and should only be used when you'll otherwise hit maximum, or when you'll still have enough for the next DP / DA+CaS if they're about to come off cooldown.

Wait, wait! On single target if you have to choose between DA+SE or DA+DP you choose DA+SE D: 140 more potency compared to additional 100 and blind.
Of course, you should conserve enough mana to buff CnS, but you speak about perfect situation when you can hold static 30% mp without intrusions, i of course had in mind situation that has gotten out of control due to anything.

The DoT would fall in line with the lore of Dark Knight. It would also give us some sort of sustained heal while damaging an enemy, similar to Mercy Stroke but a different flavor/style. Yeah, it could be worse if the damage on that one mob actually dies before the tick goes through

Actually once the mob die, DRK could regain remaining DoTs timer in an instant. Oh! Like Thundercloud for BLM is working, if you know what i mean. But i quess that would be OP. Ultimate healing.