Everything's solid about BAT. But as you highlighted:-

However, one thing which is very blurry and the team doesn't really provide legitimate explanation either is which marketing companies want to work with Brave. When now the user also get a fair share less goes to the publisher and advertiser. Is that something to be satisfied with?

Blurry territory indeed. Steemit has been operating without ads, so maybe it's not all that required, but still, i think advertising will be around no matter what. So far BAT seems to be an okay solution, never seen such a thing before. I think it's worth supporting (and risking your funds for a potentially great returns)