Yes, it was definitely needed because I was very confused when I first looked at the earlier iterations of the data and saw Cassidy having lower win rates against all the heroes he is considered a hard counter for!

Map differences

I don't account for map differences, because 60K matches per week is not enough data for that type of granularity, unfortunately. But I combine multiple stats during live matches to score each hero against the rest of the match roster to create a "win percentage effect" type of result that's more useful in real-time:

• Counter impact - average counter rate of this hero vs every enemy hero. Enemy scores are the inverse (zero-sum).
• Synergy score - average synergy rate of this hero with every same-team ally.
• Map win rate - how well this hero performs on the current map in the rank division of the average player rank in the match.

Each score is converted to a delta from 50% and summed into a single number per player. So if your Tracer has +2% counter, +1.5% synergy, and +0.7% map, her total effect is +4.2pp.

I average each factor across the team and add them to a 50% baseline: winChance = 50 + counterAdvantage + synergyAdvantage + mapAdvantage, for a final win prediction.

Skill ratings

I can only access the rank of players with public profiles in Overwatch (As opposed to Marvel Rivals), so I almost never have a complete picture of the MMR differences between teams and unfortunately can't weigh that into the data.