Thanks for the response, Hellath. Yes, that makes sense. As for the higher rewards with higher difficulty, well, that's not usually the case in practice. You end up scoring lower overall because the difficulty scales higher than the amount of credit it gives you for completing at that difficulty. It seems to be slightly better now after this patch, but it's still way lower than it should be, imo. It feels like you're punished for doing well.
I would recommend maybe disabling the mastery pop-up, it's unnecessary. Unless you want to reflect this rating in-game somewhere.
Edit: I just want to clarify what I mean about feeling punished. Gaining mastery is inevitable if you want to win matches, which everyone does. We don't seem to get enough credit for the difficulty in the scoring phase. Additionally, as the difficulty escalates, your winrate drops when you get above 60% difficulty, so it just feels like an inconvenience most of the time. I feel like gaining difficulty should proportionately improve your rewards to compensate for the losses you might face at higher difficulties.
On a sidenote, doing the new campaign maps at 60% difficulty is quite lame, dealing with the new mechanics and players at that difficulty is rough. Could you maybe bump down the difficulty of the first level for the first few weeks to compensate for people learning? Or make difficulty map-specific. All these new players trying to learn the map at that difficulty usually results in a loss.