I had a couple interesting thoughts cross my mind and thought I'd throw them out there. I can't say I've read ALL of the Drk suggestions but this is kind of a culmination of what I've gathered, and while not complete, maybe it's enough to help spark some other ideas or fine tuning.
Without further ado
Dark Arts
The main change to this is an effort to reduce the "spammy" feel commonly complained about. Instead of directly buffing a particular weaponskill or ability with extra potency, I propose it mainly be limited to combo finishers to achieve additional effects which will otherwise be modified from their current form. Such as:
Dark(side) Blade: Increases damage dealt by 20% for XX seconds (take away Darkside skill and have the damage effect be gained from finisher combo)
Delirium Blade: *either* reduces CD for blood weapon / blood price or increases duration blood weapon / blood price (take away Delirium and have the effect be gained from finisher combo)
(need something else for 3rd combo, perhaps Souleater combo that restores portion of hp outside of grit? lol.. Or how about giving DRK an exclusive damage down for party utility? Could be at the end of a "non-dps" combo so it's not a gain to always keep it up, and short duration of like 5 seconds so it's not up 100% of the time, just something you can time right to reduce party damage by 10% or so)
Obviously there would need to be adjustments so it's at minimum on par with current damage combos. Mainly just trying to make the kit more interesting than just "press this button", giving the weaponskills more synergy with the entire kit.
Additionally, I'd propose a stacking effect akin to monk or samurai. Either directly related to performing each combo or just simply stacking them 1-2-3. I was thinking of something along the lines of each stack increasing blood generation by X% so you could work to build this up then go ham with bloodspillers. And perhaps another ability that could convert those stacks to MP or HP. Or, even more interesting, tie the stacks into Carve & Spit, which could deliver an actual 1, 2, or 3-fold attack based on the # of stacks spent (something that could encourage you to build & spend vs build & sit on)
Blood Price
Obviously Blood Price and Blood Weapon should be free to use whenever, not limited to stance. My suggestion for BP is fairly simple, basically the same as now restoring a bit of MP, but let's also add some HP restore, and how about some Reflect damage to keep things interesting. (I think the potency would have to be lower than Vengeance if it's going to remain a short CD)
Living Dead
Sacrifices all but 1 HP to create a Dark Shadow for 10 seconds. The Dark Shadow will absorb all damage taken for it's duration, up to it's maximum HP. If after 10 seconds the Dark Shadow is not destroyed, its remaining HP will be restored to you.
So, just a few things I thought about. Please discuss!