I think the concept is fun enough (popularity contests can be interesting), but the execution is just bad from the beginning.
They can be interesting, but as it stands now they add no inherent value to the game. Yes we all need feathers, but you get them from everything regardless. The mode needs something more to make the time spent worthwhile. (And it needs to better respect the time of the players.)
Would be cool if the winners were put into some sort of hero fest banner with higher percentage for focus 5*s or promised a special unit at some point in the future (though all the winners sans Elise have a special unit out now or in the horizon).
That or just throw orbs in somewhere.
That would be cool, but all the winners so far have been the uber popular (female) characters that will be featured heavily no matter what.
I think they should alternate between this type of Gauntlet, with some much needed procedural changes, with a Gauntlet of 8 totally new units. All they would do is reveal the characters themselves and their weapon type, but no info on their skills. Then don't have any banners yet, just start the Gauntlet. Whomever the last two characters left are, offer them both as prizes for players. No matter which team you join you'll get a character afterwards, the losing side getting a 3* version of their chosen character, and the winning side getting a 4* version of their chosen character. These characters would have all their skills locked behind their 5* rank so all you get is a weapon and a blank canvas unless you want to invest in them.
Then whichever unit wins, they can include them in a special post Gauntlet banner (preferably a skill focused one so it still has general appeal), ahead of a planned regular debut alongside whatever other characters would normally debut with them. (All eight characters would all be added to the game eventually via normal banners, but this type of Gauntlet would provide an opportunity to nab someone early.)