There is class-exclusive gear, even for crafters. Whether you use them, or stick to a set equipable by all classes is up to you.

DPS, definitely not. There's a lot of class-exclusive gear at end-game, but even before that, there's light and heavy armor. For example, my Lancer/Dragoon gets access to a lot of heavy armor that GLA/PLD and MRD/WAR can equip, but Pugilist/Monk or Archer/Bard cannot. A lot can be shared, but definitely not all.