Just to add to the above comments, I did it with a rather pedestrian team (team score 3,704). I got Survivor III (finished damaged, with 1 or less life) with my Knight Coronet (level 17, ultra-rare). Match stats were 53 skull damage, 77 spell damage, 32 damage. I was tier 6; it was the match that pushed me to tier 5.
I wasn't expecting it at all, especially since I haven't leveled my troops terribly much compared to others. I just wanted to pass along that you don't need a super team to do it, just a bit of luck.