For me, personally, I see the Gauntlet as a game mode where I have to build up my roster so I can take on the stronger challenges down the road, not a game mode where I should be able to conquer all of it right now. More new characters will be released and our rosters will gradually get deeper.
At the same time, I totally understand the concern that perhaps there are rewards being offered right now (even if it's just a beta test) that are mathematically impossible to attain. If that's the case, yeah, it should be addressed.