ORIGINAL: ubiquitous
I played this through a couple of times as allies and achieved a minor victory on both outings. I think it will be quite hard to get a significant margin of victory, but I regard this as somehow realistic: I think that shortly after midday on the 6th June there was a sense that things were going the allies' way, but nothing like a decisive victory by such an early stage and still a very real uncertainty about whether the invasion would work come undone. Curious to hear your experience.
I've learned victory conditions are a difficult balancing act.
From the German POV at D-Day, the strategic focus was making any strike against the Nazi fortress Europe appear futile and costly enough to sap allied will to continue the fight. Immediate tactics should be to contain any incursion onto the continent and force the residual force into terrain where it can be destroyed in detail.
From the US POV at D-Day, the strategic focus was to gain a useful lodgement on the continent within which a counter attack can be assembled in a relatively safe manner. Immediate tactics should be seizing key terrain in the landing zone to facilitate strengthening the toe hold with follow on forces.
Balancing the number of points awarded for attaining those different goals is the critical exercise in balancing the scenario.
I think playtesting should be conducted in two phases.
The first determines whether the forces interacting are conducting their operations in a manner that reflects the historical reality of the situation. In broadest terms it determines whether the locations selected as objectives are achievable as a human player and drive the AI to defend in a manner that is realistic and challenging to address from either side as the human player. While I realize supply isn't part of your consideration during a relatively short term operations, if one were to include longer term operations that demand implementation of supply operations as a consideration, it also would be used to determine that the entry points and the supplying operations were capable of sustaining the engaged forces over a longer term in a manner that reflects how they were able to fight during the original operation.
Once one determines they get a combat that reflects the historical record, then the parameters of increasing supply, changing the weather, altering the reinforcement schedule can be applied to add or subtract capabilities to opposing forces so a player can construct combat in a manner which addresses that player's personal skills and desires for complexity.
The second would be used to refine the rewards / awards for addressing different victory objectives. In this particular scenario, Germans would be awarded more victory credit for inflicting casualties on the allied force than the allied force would receive for inflicting casualties on the Germans. Allies would receive more victory credit for taking geographic locations to allow follow on support at the end of the combat than Germans might receive for holding those same objectives during the term of combat without inflicting many allied casualties.
This is the way I break my work into "chewable bites" as I work on a personal scenario. I'm more comfortable breaking processes into more finite steps than trying to solve everything at once.
Hope this helps.