1) I would, definitely, delete all 3rd classes, create another classes more balanced as well. Nothing like this, that only use 1 skill and KO.
2) Update the graphics. It's nice, i really like the anime based sprites, but they are kinda outdated. Nowadays, they could work in a new graphic engine.
3) Create new instances that could be nicer. Most of the instances are: Walk, walk, walk, talk to npc, kill monsters (only using 1 skill), repeat. Do it 100 times and you'll have an OP item. Something that really need skills and team play would be cool.