http://amdapori.tumblr.com/post/1518...thats-fine-too
All I gather from there is that the first dark knight forsake the shield, so the greatsword might be used for its size allowit to block blows more easily
the same blogger also posted the lore on BLM, WHM, SMN, SCH, AST, PLD, WAR, DRG, and MNK. basiclay everything but the ranged melee
