here is my .2 .  After watching it I thought, huh, the audience didn't seem to get it.  Then I thought, I bet if they had performed Mystery Train, or Sweet Hands, or even Apologies..there would have been a completely different response.  I like it, I don't love it.  The song does not showcase Grace's amazing voice like other songs do.  (the end is killer though!) Them having to cut it down to 3 minutes I think affected the overall performance.  So if they'd have asked my advice, I'd have said don't do Tiny Light...not on Ellen, and also don't make it their 1st release off the new album.  
BUT WHAT DO I KNOW??  :)