Every time I see a detailed post here, on Reddit, Discord, or elsewhere talking about the gap in self sustain, I see people clamoring to post "skill issue."
No one is saying all tank jobs should be the same but there is clearly room for adjustment.
The whole point of "wall to wall" is to be as efficient as possible, for the sake of everyone's time (the most valuable of all resources). WAR scales its self sustain/mitigation based on the number of targets, and actively heals itself WHILE contributing AOE damage. This is the most efficient combination possible.
DRK tends to be the opposite. The more targets the worse its tools tend to get (mainly due to the full minute CD on Abyssal Drain), The Blackest Night (while a fun and useful ability) is definitely lacking compared to the WAR equivalent Blood Whetting.
1) It actively takes away from their damage as it competes for MP while also being on a cooldown (unless it breaks, which it frequently won't due to random enemy channel attacks and a short duration).
2) It has a 1-shot 25% health mitigation while the WAR ability has only a slightly longer cooldown, does NOT compete for or cost ANY resources, and can completely fill their health bar multiple times over in AOE.
Putting Abyssal Drain on a 30sec CD would help a little, but not much. Another possible solution would be to modify how TBN behaves when the shield breaks:
1) Have breaking the shield reduce the remaining cooldown on TNB by 10sec and refund half the MP cost. EDIT: Having played this more a CD reduction on TBN from breakage would be marginally useful since gaining enough MP to actually use this would be a challenge. Plus the refund seems convoluted.
EDIT: A better option would be to have breaking TBN reduce the remaining CD time on Carve and Spit & Abyssal Drain by a certain amount (5-10s).
2) Have breaking the shield apply a minor heal over time effect.
EDIT: Sorry this post was really bad before, I was apparently having a really bad day.