I have to disagree, I think that randomness is what defines this game, particularly because it is a DnD game.
Each play through may yield a different result, even when the same actions are taken, specifically because this is a game of chance. This makes the game more exciting, because you don't know how things will play out. Missing at an inopportune time may force you to come up with creative strategies to rectify the situation, while getting a critical hit might save you in a fight that you would have otherwise lost. The variability of each round makes each fight unique, even after several play throughs. The game would be far too simple and repetitive if it just became a game of addition and subtraction.
And while bigger chances to miss are particularly noticeable at lower levels, this often is reduced as the character gains levels and more powerful magic items, because of the "bounded accuracy" philosophy of the game.
I don't think this game should emulate DoS combat, because this isn't DoS3, its is BG3, based on DnD 5e. I think developing this "system of averages" would not be a wise use of Larion's resources, and would actively detract from what is a defining feature of the combat system.
