I feel like DRK is in a good place right now, but that's generally only at 70+, when we have TBN. DRK's defensive options until then are extremely lacking. Dark Mind is really bad, Living Dead is situational, at best, so that leaves DRK with only Rampart and Shadow Wall until TBN is gained. TBN itself feels like a double-edged sword. It's shield is massive allowing you to absorb almost anything, but if it doesn't break, then the MP was mostly wasted. Then it also has the problem of being a centralized part of DRK's cooldown cycle that everything else defensively is lacking. Things I want to see:

A mini TBN before 70, learned really early, that has many of the same effects but only shielding for 5-10% of max HP. This way, we still have the functional benefits of TBN even at lower levels. Additionally, TBN's shield effect gets dropped to 15% of max HP because 25% is just too good and leaving the rest of the defensive kit lacking. Blood Price could be this mini shield.

The return of Dark Dance/Anticipation and roll it into Dark Mind. This way, you get a Physical Defense buff, and a Magic Defense buff, but weaker overall than Rampart/Camouflage. Gives DRK another button to hit in lower level dungeons/pulls that aren't -sigh- Arm's Length (don't get me wrong, the change is great, the cooldown is just massive, and I still feel like I need another defensive to hit).

Similarly, I wish Abyssal Drain was made the combo branch off of Unleash which then upgrades to Stalwart Soul, or at least maybe give it an MP regen on top of the HP recovery. Maybe make it an alternate AoE MP spender, not unlike Flood of Darkness/Shadow, where you gain HP instead of Darkside. It does basically the same thing, but sometimes that HP regen is more important than the damage refresh.

I realize I'm not a lv80 DRK, so I may not have room to talk, but these areas are where I feel DRK lacks the largest. DRK just feels really bad without TBN, and it doesn't feel that much better without Stalwart Soul.