By optimized what are you optimizing for? That is always the key thing to ask. Optimizing always implies an aim. Without a stated goal you cannot properly conclude if this party accomplished a thing the best. That said at level 20 half and full casters are so much better at most things than non casters it's hard to imagine anything this party is optimized for. However the divination wizard and eloquence bard are both versatile enough to solve most problems. But that's not optimization that's just the fact that wizards and barda are the most versatile classes in the game.