Solo speed runs and Iron Man mode have never appealed to me. With that part out of the way, "powergaming" has never been necessary for me. In a solo game, I'll tend to play a reasonably balanced character. In party themed games, I'll build my party around my main character. With the Divinity limit of four characters, a well balanced party might be difficult to pull off here. I'm a completist, too, so I tend to make and develop my characters around experiencing as much as the game as possible.