I don't remember about numbers, but your characters sound a lot stronger than mine, I only had Tier 1 weapons and I've never fought an Adamantoise, so I reckon you're strong enough to defeat the last boss. Here's the strategy I used:

Party: Lightning, Hope and Vanille.

Starting Paradigm (used for defensive purposes): Convalescence (2 Medics and a Synergist). Lightning and Vanille heal, Hope buffs everyone (make sure he has at least Veil and Haste). I also use this when the boss uses the attack which brings everyone at 1 HP.

Tri-Disaster (3 Ravagers): When everyone has been buffed, I use this to break the boss.

Ruthless or Smart Bomb (Commando/Ravager, Ravager and Saboteur): When you've broken the boss, debuff him and increase your damage bonus. If you want to end the battle quickly, cast Poison on him until it hits because it will seriously hurt him. When you've got the damage bonus up to 600-700% or more, switch to...

Relentless Assault (Commando and 2 Ravagers): Lightning attacks, the other two raise the damage bonus to 999%.

Repeat this until the boss dies. Recast Veil if it wears off because it protects you from status ailments. If you get hit by the poison status ailment, immediately use a summon (if the boss uses the attack that brings everyone's HP to 1, you're dead), as that will restore everyone.