Seeing UBERHAXED DRK, I'm gonna make my own since the skills he listed are overpowered.

Dark Knight (DPS)
Class: MRD
Secondary: Thaumaturge
Tertiary: Archer

Cross Class: THM mainly for Thunder. Swiftast+thunder = another AoE. Archer because of Raging and Quelling.

Job skills:
30 Dark Seal - Removes enmity multiplier from moves, increases damage dealt and taken by ~10% (or rather whatever puts it on par with DRG and MNK).
35 Soul Eater - Next action skill has double potency, but takes 5-10% of player health.
40 Guillotine - 300-400 potency off GCD, 1-3 minute recast. Adds 15 second DoT.
45 Blood Rage - Increases damage taken and dealt by 15%. Increases Enmity to all targets. 2 minute recast.
50 Blood Weapon - Increases damage dealt by 15%, each hit recovers some % of HP. 10 second duration, 5 minute recast.