What made you think that the rotation of the dice is somehow important? We're honestly very curious. We are stunned.
Both the enemy units and player units perform attacks on the Y axis(enemies attack down, players attack up) The only exception are archers that can attack any unit on the map.
You can right click on all dices and enemies to learn about what does what. That is stated right in the beginning of the game in the splash screens/tutorial. (Also you can learn how attacks work by looking at how enemies attack you)
As for the 'useless' dice, the decision of leaving dice in the pool of options after the unit's death is intentional