I wanted to highlight a major problem with DRK that I've noticed more frequently as of late.
I can sum up this problem with a simple if-then statement with variables.
"This ability gives you x, but if y, then z."
-Where x is a seemingly very beneficial effect, y is a condition that is often either A) partially or completely outside the DRK player's control or B) a scenario that is overwhelmingly commonplace compared to the alternative which would render x intact, and z is something bad, a penalty, or punishment.
There is also a smaller, sub-problem to this, wherein DRK abilities are complicated in a way that conflicts, directly or indirectly, with attempts to balance them, by amounting to excessively complicated expressions.
I.E.
"Ability a costs b and gives you c with an additional effect of d"
-where d is the only actual effect of the ability, and b and c cancel eachother out when the expression is simplified.
Living Dead:
"This ability does gives you [invulnerability], but if [you are not healed for a value equaling or exceeding your maximum HP], then [you die]."
The Blackest Night:
"This ability gives you [a 20% HP shield], but if [the shield is not completely consumed], then [its DPS resource cost is not refunded/you lose 140 potency]."
Sole Survivor:
"This ability gives you [a chance to get a 20% HP/MP heal], but if [your target doesn't die in 15 seconds], then [it does literally nothing]."
Dark Passenger:
"This ability gives you [oGCD damage], but if [you're not in Blood Weapon and about to drop a Quietus that will cap your MP and then some, or tanking 10 or more mobs], then [it costs 1/4-1/2 of your mana for relatively insignificant potency]."
On the second, "sub-problem" the most obvious culprit is Delirium.
"[Delirium] costs [50 Blood Gauge] and gives you[2400 mana] with an additional effect of [+8/+16 seconds on Blood Weapon/Price]."
The Blood Gauge and Mana cancel eachother out - the only thing Delirium actually does is buff Blood Weapon by 8 seconds...
... this literally makes Delirium just a shade over half the gain of the Blood Weapon you buff with it, while being on triple the recast time.
.......
Soak that up.
Delirium is half as powerful as the Blood Weapon you buff with it, and has triple the recast.
.......
To put this in perspective, this would be like Inner Release being a +30% attack power increase for 10 seconds on a 180s cooldown.
TBN suffers from this same issue.
"[TBN] costs [2400 mana] and gives you [50 Blood Gauge] with an additional effect of [+20% HP shield.]."
All it really does is give you a 20% shield, but this is compounded by the fact outlined above - sometimes it'll also cost you 2400 mana.
*****
Anyway. That is all. Just wanted to highlight what I have observed to be some patterns in DRK's many problems, namely, its abilities are deceptively weak given resource conversions disguised as gains, and arbitrarily punishing abilities reliant on meeting conditionals to not leave the player in an equally bad/worse spot than had they not pushed the button in the first place.