Opening up Lancer gives DRKs access to Blood for Blood, Keen Flurry, and Invigorate.
-Blood for Blood: In the OT position you sacrifice your defenses for increased damage (stacked with Darkside +25% damage). In the MT position you have the option to use BfB for increased damage at the cost of losing the benefits of your tanking stance. (5% incoming damage for 5% outgoing damage). This would give DRKs a “built in” pseudo stance dancing ability alleviating the problems with Grit being on the GCD and having such a high MP cost. A change here would make the DRK a dynamic tank to play where you can put yourself at risk for increased damage potential, which I think better reflects its lore.