DRK an easier tank?

[Phoenicia]

PLD actually would be the easiest because you don't have to manage your MP on PLD to maintain enmity.

You don't have to manage your MP on DRK either. Power Slash is by far the most potent enmity combo out of the three tanks and it costs no MP. So even without Darkside, DRK would probably hold more enmity than PLD.

Both PLD and DRK need to "manage" their MP for AoE enmity.

But tanking difficulty isn't about holding hate. Since holding hate is the easiest thing in this game.