TBN is without question one of the best mitigation tools in the game, but if you're crawling on bloody hands and knees getting to the finish line that is level 70, something's not right. Far too often I see DRKs only using Shadow Wall and Rampart like it's their only tools. And these are the DRKs that typically gripe about being so squishy. If you've become proficient with self-sustainability prior to lv70, TBN is even better than advertised when you finally do get it. DRK isn't any different from any other tank in terms of becoming better at what they do the higher level you go. Optimization of the tools given to you throughout is going to make life easier on you and your healer.

At level 50, you are no different from the other tanks when it comes to role skills. You have Anticipation, Convalescence, and Awareness and you should be using them. I don't see DRKs using skills like Anticipation and Awareness during the pull. They instead wait 2-3 seconds after getting wailed on to use them. Taking more damage from behind is still a thing last I checked, along with an increased rate of taking critical hits. You can still parry while facing away from enemies so rotate Anticipation with Awareness during the pull, and pop Convalescence along with a defensive CD like Shadow Wall or Rampart when you come to a stop because this is when damage will be the highest. These are things all tanks should be doing because they all have access to these skills at the same levels.

Along with what I have mentioned above, I don't see DRKs using Blood Price during the pull either. Again, they wait until stopping to pop it reducing the amount of Unleash/Abysmal Drains they can cast during the most opportune point of the pull to do so. BP will help restore the MP used from Unleash and Unmend. It will then be on cooldown by the time you stop so you won't have worry about stuns from the group making it ineffective, plus you have a stun yourself and full MP gauge to do what you do.

To continue with more DRK specific abilities through level 69; against magical enemies, you have Dark Mind, which no longer requires DA and you should be using it. All the while I am not seeing DRKs use DA+Dark Passenger. This IS a mitigative tool which causes AoE damage, builds hate, and blinds enemies. You should be using it. I'm not seeing DRKs using DA+Abysmal Drain. This causes AoE damage, builds hate, and restores HP. This is a self-sustaining tool and you should be using it. Once you use it on a large pull, you'll never not use it again.

There's a lot of MP management during all of this, but that is what makes DRK such an engaging job to play. It doesn't have the same defensive capability as a PLD, but that is the intent behind its design. It's designed to be a very offensive minded tank that also builds aggro very quickly. It is an absolute AoE monster that definitely shines during large pulls. Don't be afraid to use Living Dead either. It's another defensive tool at your disposal, and I would not wait till you're at critical HP to pop it.