Assassin MK Sorcerer Ranger Warrior MA Strider - Mage - Fighter <---- All completely useless(- Augments), since other classes do the same thing and more. Mage is an exception, but still fairly useless.
They are fairly balanced overall, and each has it's strengths and weaknesses. The only really notably lacking class is warrior, in my opinion. It's a tank that can't block. It's most powerful attacks take forever to use, and a sorcerer could pull off an equally damaging attack at range with an AoE before the enemy has even aggro'd. Or just high exequy for single powerful enemies. And just as a final insult, warriors get to equip half as many skills as any other class.
The main reason I put sorcerer at the top is for it's ability to stunlock even the Ur Dragon to death just by holding and releasing square every two seconds. Then there are its various mega-nuke attacks and Exequy.
All puns intended, especially sexually suggestive ones!
I'm no game-breaker or Min/Maxing, so I couldn't care less about what is "strong" or "Good", seeing as this game is easy enough for any class.
So far out of all the classes I've tried;
1 - Strider; I love the speed and agility these guys have. What they lack in power they make up with grace. 2 - Assassin; More power, less grace than a strider. Though I've only used assassin with Daggers/Bows as my setup. 3 - Mystic Archer - VERY cool and neat, I totally felt like a quincy from bleach. Though seeing as my first play through was a rogue/Bow focused, I did feel particularly left out since I didn't have any Mage/Sorc augments. 4 - Fighter; One of the few games I actually like being a fighter despite being given a choice of mage or rogue. 5 - Ranger; Definitly stronger than Strider/Assassin, and their bow skills are epic! Though sadly, their lack of mobility was abit of a turn off for me. I prefer Strider/Assassin's nimble-ness compared to Ranger's raw strength. 6 - Mystic Knight; I enjoyed Fighters more than MK so far...But granted, I'm only rank 5 and hear that MK gets their good skills later on.
I haven't tried Warrior, Mage or Sorcerer just yet though.