I play the game primarily for enjoyment, and at some point no reward will make a difference and it’ll be purely for enjoyment, however with proper game design the risk and reward should correlate pretty strongly. Even if the game is fun, even I personally don’t care, fact is that you are dictating player behavior to some degree when you have serious reward inequities. The same way the chest power cutoffs push you into the next difficulty ever so gently the deed rewards being bad push you away from them. It won’t stop you or dictate your play on it’s own, but it provides impetus. Powered chests are debatably good game design as it keeps pushing the player to get better, continue being challenged, and stick with the game longer. Deeds are bad game design because they cause cognitive dissonance as you have to decide between efficient progression and having a fun challenge, when by all means it should deliver both (if successful).
As long as loot is part of the game, and as long as loot has an impact on the game, loot should be balanced in an equitable way. Cosmetics are part of this, albeit since they do not affect gameplay the impact and concern about cosmetics is VASTLY lower. Not completely unimportant, but more of a minor QOL issues than a central game design issue. That being said if skittergate had a 50% chance of rewarding a cosemtic, you can see what player behavior issues that would cause, so cosmetics are not completely irrelevant either.