HT Games
Using a Controller With Auto Fire
This trick will require a PSX (or PS1 era controller) with an auto-fire feature. This is because you will be using the Spark Net item a first tier lightening item. First and second tier items require you to press it as many times as possible to up said item's damage against enemies. An auto fire controller will both save your fingers and get as many shots at the boss as possible.
Start the fight with Rose, Dart and Meru, equipping Meru with the Therapy Ring, Rose with magic stat increasing items and Dart as is. When the fight with the Divine Dragon starts, do not go into Dragoon form. Instead, have your party attack the Divine Dragon; Dart using only his Additions and having both Rose and Meru using Spark Nets (while turning on the auto fire on your controller for each use).
Dart-Only Attacking
Another way to take out this foe is to solo him with Dart only. This tactic requires good timing with additions and knowing how to play Dart almost flawlessly. Go into the fight with Dart, Miranda, and Kongol. The other two will die; this is okay as Dart can do this alone. Take out the Divine Cannon first, guarding when it is about to attack. Do this, then go onto the Divine Ball, leaving the Body for last. As long as you go in this order and get past its Claw stun, soloing this boss is doable.
Using Group Magic Attacks Only
You can also go at Divine Dragon as a caster centric party. Pre-battle, purchase magic attack items that hit all enemies, such as Night Raid. During the battle, do not do your normal attacks or additions, instead use your purchased magic item to hit all three parts of the Dragon. For example, using four to five Night Raids (at 180% or more power) will end up killing off the Dragon's Ball and Cannon and do great damage to the body. This will leave the party a gravely hurt Dragon with only its fear inducing screech and leg sweep.
Simple Kill Method
If you simply want to kill the Dragon, no hacks with controllers, no cheating by exploiting a lone party member's strengths or using a stock pile of items best used elsewhere, there is a way to kill this boss fair and square.
Walk into this knowing that using Dragoons is off limits for this fight. Have Dart, Haschel and King Albert as your main team. Make sure these Additions are leveled properly: Madness Hero (level 5), Hex Hammer (level 1 or 2) and Flower Storm (level 3 to 5). Equipping the Bandits Ring on Albert, Attack Badge on Dart and the Therapy Ring on Haschel will greatly help. Have Dart as your main healer, only allowing him to attack when everyone is topped off, while having the other two be your main attackers (healing them if necessary).
Always kill the cannon, ball, then the body itself in this order. The cannon deals massive damage to two players while the ball leads to a damaging group attack. Taking these two items out makes the fight easier.