I think the best recipe is that every class can have fun to run when they have invest some time, gold and money into their characters, i think we can all agree that tedious mechanic is fun for couple of days but become very boring after a while, so the best would be to make every class be able to be op and have fun running

Ps: Somberholt was the most fun expansion imo especially with tb and later on with ebon aegis hehe (this is from a warr perspective, idk for other class)