Honestly, class fantasy can only go as far when you're playing your role in a team in multiplayer game. In a single player alone sure, do what you want, but in a party with other players you can't just go "in my mind this classs should be doing this so I'll play like this", you play it like it's supposed to be played it. Outside of roleplay, you go by class mechanics as designed.
And if you don't like how a class workds becaue it breaks your fantasy...play another?