New Job abilities like Hasso or seigan except with drk they focus on Physical or magical damage. Physical JA should increase weapon damage, ws damage (which is already increased from previous ability) and Critical Damage (Thought this would mesh well with the theme here) and it should also increase casting/recast time and mp cost so as to make you want to focus on melee damage. Magical JA should MASSIVELY increase Magic attack, lower cast/recast time and Occult Acumen, this way you can get tons of tp from the chain spell blasting and then unleash those magic attack based weapon skills like Herculean Slash for considerably greater damage and effect. As for downsides for Magical side major decrease to weapon speed and damage should suffice.

Also SE need to stop making everything so resistant to Dark magic just cuz they hate that people use sleep to gain the advantage on a monster. They also need to fix abyssea so that drk can use absorb - STAT spells while having cruor buffs on (also HP boost from Drain 2) and increase the stat drained by skill level so that a drk at our current level can drain 50 of each stat from opponent. Also need to look into the following ideas for new spells and abilities

Absorb Attack
Absorb Defense
Absorb Evasion
EnDrain - make it really strong so that we can actually justify using souleater
EnAspir - stronger than dnc's ability
JA "MP Attack" - Souleater that uses mp instead of hp to increase dmg plus its not gimped (Yet)
Enspells 1-3 - Yes i know i put 3 on there but listen I have always thought drk was based on usin magic to increase their power and thats what enspells do, as for rdm they are mages that can hit, at least let both jobs benefit from these spells.