I see that some people think that STR builds are overall stronger, but that's a heavy misconception and here is why:

First, I'll address the fact that people only think that because of the Ethereal Greatblade and nothing else, because that's really the truth. But the weapon isn't really broken (besides its skill, which not only causes some heavy damage but makes you invincible), but more so on the convenient side: it has great damage, range, scales with only 1 atb and can be found kinda early in the game.

Seriously, everything is just too strong, think about it. Some spells can easily delete bosses with no effort and you can have access to near infinite stocks of "mana potions". There's a dark fireball spell that is comically stupid broken, it can easily 2-3 shot bosses and elite enemies.

Instinct can give you near infinite resources, you drop so many healing injections because of it, not to mention that the attribute "power" is tied to it, and the MOST BROKEN mechanic in the game (SPOILER ALERT) is tied to this attribute: the transformation. That transformation can evaporate bosses in a fraction of seconds, I literally had to avoid using it when I got it because the bosses felt like basic ass enemies.

For real, the most basic builds are the dex builds, but even they are very strong overall.

The game isn't really difficult. Besides the final gauntlet of bosses, that being Laddak, the 2 sisters and the secret boss; all of them are very easy and you'd have to intentionally try to make them hard to have a challenge.