My take on the art style (old vs new)
I just played all content in a row yesterday, so I saw both variants of the art
The original art was more unique and different, but all characters really looked the same, with very minor changes
The new art, while more unique per character, was achieved with a very different art style for each character, meaning that the game no longer has a cohesive art style
My suggestion would be to decide on one specific art style for the entire game, but to make sure that each character has a unique enough look
Once you decide on a style, I would highly recommend that you re-generate all images in the game to the new art style, and stick with it for future updates
It'll take some time probably, but it'll give you a time to go back, fix the issues with the game anyhow, and come back with a stronger product overall