Some people me included wants that to change. Its not fair to beat a ai5 and get less than what you get from ai3.
I wish the win gain were fixed instead (double reward for EM as always), but instead there were many smaller benefits like, playing only cards from one element +3 coins, only use spell and perms +3 coins, end game with 50+ surplus quanta +3 coins etc. The rewards or bonus needn't be fixed either, they could fluctuate between 1-5 coins and the bonuses could change from month to month or similar to make decks change and evolve.
I know its practically impossible with how the game is built but nevertheless.
At the core lies the following; I consider the return of
in relation to how much HP you have left to be a wall, a block in deckbuilding, a factor that penalise and limits the possible diversity of decks while playing vs the AI.