Few role playing video games have ever truly captured the notion of strategy, at least until Bravely Default. I had maxed out all the levels, mastered all the jobs, and gotten most of the best equipment long before the final chapter. I thought that this will make the game so boring after this, and that every encounter would be too easy to bother with. I was never so wrong.
Going through all the abilities for each job class, I discovered that there is no "ultimate" setup, and that the enemies in the later chapters are not dependent on their stat values either. Now the game requires pure strategy to progress, no more mining for the best of things, you have to set up each character and their gear to fit into any given situation, a specific area or boss. If all your characters are the same, you will fail.
One of the best classes is the salve-maker, great for healers and attackers. The item attack items do a constant damage value, not based on stats or levels, and they ignore the default action. Attack items always do the same damage, only effected by weaknesses, making them a consistent method of reducing the HP of enemies, as they are also not effected by the number of targets.
For the healer, the medication ability offers a cost-free method or raising all allies. Combined with the healing boost from the salve-maker and using the blessed shield, your healer only needs a good knight to cover them. This is where your variation is a must, a good knight character can protect your healer from many attacks by using the full cover ability, and a ton of defensive equipment. Then give them revenge from your red mage job and they can do full cover with powerful attacks.
The key is how you mix and match your characters and their abilities, the equipment has less of an effect at this point, they depend on their support abilities the most. A knight with dual shield can become invincible, but will offer no real damage to the battle. A healer with salve-maker can keep everyone fighting, but will never have the time to use their offensive abilities. A thief can help with gaining a lot of items from the opponents, but will need a secondary job to become useful in battle, like black mage or vampire.
The one flaw with the strategy system at this point is that there are so many ways to accomplish things, so many variations and builds that can work, there is no "ultimate" combination. You will have to experiment, play around with various arrangements, to find what works best for you in which situation.