I'm pretty happy with where PLD & DRK are.

Both tanks do roughly the same damage against dummies out of tank stance. As DRK I do about 5% more damage out of Grit than a PLD in Sword Oath with both in the exact same tank sets with the exact same attribute placement. However, pulling that DPS is 100x easier as PLD. PLD only rely on TP, and a good portion of their damage comes from the boost to auto-attacks. As DRK I have to manage more abilities, buffs, and MP.

But there's more to it than what you can do on a dummy, or as OT which you will almost never be. While MT out of tank stance DRK will pull further ahead. The main two reasons being that A) their resources(MP) regenerate much faster while taking damage, and B) their hate generation with proper use of Dark Arts+Power Slash is much higher than anything a PLD can do. This allows them to focus solely on damage after the initial pull, and to do more of it than they could on a dummy. This goes for tank stances too. A DRK not being attacked will eventually fall behind a PLD in damage due to lack of resources. Also worth the mention that DRK takes less of a hit dropping Grit than a PLD swapping to Sword Oath, though there is still some delay because it is tied to GCD. In contrast, DRK are completely lacking in support abilities & Hallowed Ground.(I almost died in phase change to Living Dead earlier)

I've taken both tanks into Alexander Savage & prefer DRK so far, because it's not as boring and brings better DPS. I'm still hesitant to buy the i200 Great Sword next week because I'm worried I may want Hallowed or other PLD support skills in later turns. That is balance. It won't matter who does more once we're wearing full i210 because I'll just tank without stance & destroy everything on both.