Doing a write up on my issues with DRK, but as for what I want them to be defined as...
PLD: Healing Magic / High Defense
WAR: High HP / Party Buffing (e.g. "Warcry" would boost party's AP by _% for _seconds.)
DRK: High DPS / Magic Based focusing around Drain Spells
PLD should receive an enmity boost to Clemency and allow shields to prevent interruption. WAR should stay mostly the same, with the addition of said "Warcry" ability. DRK is the one that would be greatly changed. I'll be talking more about it in my write up, but their DPS should be heavily buffed overall to stand out as the high-dps tank.