a level 30 drk, with your proposal has:
1 Fast Blade
2 Rampart
4 Phalanx
6 Defensive Focus: Guarantees one shield block if equipping a shield, or one graze if equipping a great sword. Defensive ability, not useful unless you pull hate
10 Savage Blade
14 Spinning Slash: Swing your weapon fiercely, dealing damage to nearby targets.
18 Shield Bash
22 Outmaneuver: Slightly increases block rate when equipping a shield. Slightly increases chance of grazing when equipping a great sword. Defensive ability, not useful unless you pull hate
26 Flat Blade
30 Riot Blade
8 Enhanced Physical Defense does not increase damage potential
12 Enhanced Rampart
16 Enhanced Physical Attack Power ONLY thing that increases damage potential. also available to PLD...lol
20 Swift Defensive Focus: Reduces recast of Defensive Focus by 15 seconds. Defensive, does not increase damage potential
24 Sword & Board: Occasionally attack with your shield.
28 Enhanced Flat Blade: when using a great sword, Flat Blade can interrupt spellcasting. Defensive ability, can increase damage potential only be allowing to attack from side/behind more easily when soloing
and 3 sub class abilities.
if lnc/mrd are available: Invigorate, BfB, and Bloodbath/Feint are your most useful. BfB is the only way you have to increase your damage potential aside from your level 30 job ability.
Now compare this to MNK and DRG at level 30. Yeah...I'd never play DRK. it would be an absolute nightmare to play unless played as a tank. Can you now see why my counter proposal is more viable?