As a lover of Final Fantasy Tactics (War of the Lion ear), I would -love- to have Holy Knight. Close to short range AoE with a chance for debuffs. For armour, put them in the same classification as Dragoon, and with "Knight Sword" for their arms, making it between the Paladin's longsword and Dark Knight's claymore. Shoot, make their weapon specifically a type of bastard sword where their attack animations bounce between two-handed strikes and one-handed strikes.

Also, I've seen people mention Orlandeau. He was a Sword Saint, the combination of Agrias, Meliadoul, and Gaffgarion, and then beefed up even more. HE was OP. Agrias / Delita Holy Knight? Not so much unless you got lucky with status ailments, and we've seen how short-lived those can be in an MMO setting. A way to balance is to add diminishing returns, like with Flash's Blind effect for GLD/PLD. And then, make it so bosses are immune to the effects altogether so you don't go in with full Holy Knight teams to just cheese through a boss, though that might be a funny sight, anyway.