Nice !
I don't remember what was my exact build...
But usually, what I do is first to fully upgrade an attack die, then remove not useful dices (1 defense and 2 boost) and last add some die from level 11 or 12.
The aim is to have at least two attack dices in the end, with some boost and a bit of defense.
That way runs are usually around 10 minutes but can be less than that (current WR by Dragomadryl around 7:20 minutes).