Dark Knight needs spells like in FFXI.
It needs the Absorb-HP/STR/DEX/ACC series of spells to make it interesting to use. DRK should be a Tank/Caster hybrid after all.
And Power Slash should either return or replace Souleater.
Remove Carve and Spit entirely. The sound effect is terrible, too.
Abyssal Drain should be a spell with 3s spellcasting animation and no CD, a much stronger effect, and 3000 MP cost.
Scorched earth should drain HP of enemies inside it.
Flood of Darkness/Shadow has one of the most pathetic and awful animations I have seen in this game, only compared in ugliness to some MNK animations. It needs to be completely reworked or removed. The purpose is good, but the animation hurts my eyes.
The battle stance of the DRK is also kind of aesthetically bad. The sword should not be pointing towards the ground.