How to Beat Kirin on FF XI

Cast "Utsusemi" on every Ninja/Warrior or Warrior/Ninja before starting the fight. These players are going to serve as tanks for Kirin, drawing his attention away from less durable alliance members.

Use "Provoke" on Kirin with one of the tanks.

Run away from Kirin. Do not attempt to fight him. The shadows created by Utsusemi absorb his attacks if he gets close enough or uses a spell.

Provoke Kirin with another tank when the first tank's Utsusemi shadows are used.

Recast Utsusemi.

Continue provoking and casting Utsusemi with tanks throughout the battle.

Kill Byakko, Genbu, Seiryu and Suzaku as soon as Kirin summons them with everyone not actively fighting Kirin. They are significantly weaker than when you fought them on your way to fight Kirin. He summons one every three minutes, but never summons one twice. You only need to fight Kirin once all four minions are dead.

Cast your most powerful Aero spells on Kirin as a Black Mage, Red Mage or Scholar.

Summon Leviathan if you are playing a Summoner. Use his Spinning Dive attack to maximize your damage.

Use Barrage if playing a Ranger.

Use Chi-Blast if playing a Monk.

Attack Kirin normally with any other class and use your weapon skills whenever you have enough technique points (TP). Keep attacking to grind down his health. He does not change his attack pattern or behavior for the entire fight.