With the announcement of the new expansion, there's a lot of discussion on how the existing jobs will change in 5.0. One of the biggest influencing factors will be the introduction of new actions between level 70-80.
Unfortunately, the addition of new actions often comes along with the removal of old ones, due to hotbar space limitations. Barring the introduction of a new system designed to combat action bloat while retaining old skills (such as job-based skill/talent trees which let you choose between optional actions), we're likely going to be giving up some actions in the process.
As of Stormblood, DRK has fewer job actions (25) than any other tank (one less than WAR (26), and three less than PLD (28)), so there is an argument for removing fewer actions from DRK. But let's consider the worst case scenario.
You can add any five actions that you want. But you have to leave five behind. What do you add, and what do you discard?
Discard:
1. Unleash: This ability becomes redundant once you get Abyssal Drain at level 56. If you dropped Abyssal Drain down to level 6, it could replace Unleash.
2. Blood Price: The Grit lock isn't doing this ability any favours, and the devs seem to be struggling to balance the amount of resources that it generates.
3. Darkside: This could be converted to a trait. MP regeneration occurs when there are no active mobs (including when the boss goes untargetable to perform a special attack), and stops when there is a targetable mob in combat.
Alternatives:
1. Blood Weapon: This could be merged with Delirium to free up a hotbar slot.
2. Spinning Slash: We don't use enmity combos all that much, and this is largely a filler step to get to Power Slash. Why not branch Power Slash directly off of Hard Slash?
3. Grit: This is a fairly complex issue, discussed here. Can you redesign the tanks such that tank stance is no longer needed? If so, you'd free up a hotbar slot here.
4. Dark Mind: This is one that I'd hate to see go because of how powerful it is, but I think the whole "physical tank, magical tank" concept is a bit outdated.
Ideas for Additions:
1. Dread Spikes/Wraithform: Any time you deal damage or are hit by an enemy for the next X seconds, you recover a portion of the damage back as HP. Your actions generate additional enmity. Gives you that purple flames aura that we've been asking for.
2. Backstep/Reverse Cut: 10 yalm backstep. Resets the recast timer on Plunge.
3. Runic Blade: Absorbs a portion of the damage from the next enemy spell, converting it to MP.
4. Shadowbringer/Omnislash: Every time you activate a Dark Arts enhanced action under the effect of Blood Weapon/Delirium, you gain a stack. Using this ability consumes all stacks and removes the effect of Blood Weapon/Delirium. For every stack consumed this way, you perform an additional slash for X potency. You also deal Y potency based on the remaining time on Blood Weapon.
What other possibilities are there? You could upgrade an existing action with an new trait. Living Dead is a good candidate for a rework. I'd also be interested in seeing "counter-attack" abilities to be used following a big boss hit, like Reflect or Minus Strike. I left out potencies deliberately, because that's a balancing issue.
I just threw a few ideas out there quickly, but it'll be really interesting to see what the devs come up with.