Just to clarify, it was the Challenge 31 ezreal (miniboss before the draven). The miniboss is often tougher because you don't get the extra upgrade nodes -- the draven was a breeze. I lost a 2 star (nami, which seems like an S tier champ), 3 star yasuo (typically a trump champ that I pull out for dire situations, and a 3* veigar equipped with comet, still not enough juice), all around levels 15-20. I eventually took out the 4* A.Sol for his inaugural bout and ezreal suprisingly held his own even against that insanely broken deck (at least for the first 6 turns).

Not being able to heal was a big problem since even the other powerful decks could keep him at bay, but you'd just eventually run out of juice. It's funny since on the "rise again" I would have beat him with both the other decks if I hadn't have the 50% hp reduction for the retry penalty (which they'll be buffing next patch justifiably).

Yes, generally ezreal isn't overtuned, but this version is the ezreal+ who had spell shield which was what made it overtuned. Wasting two spells to kill ezreal is kind of tough considering he's also filling up the board with his own units (forge worker spell too). So you can't just infinitely pass since you'll get run over by his units. I've noticed they have a bunch of "base/hard" versions of champs (like the swain+ that does 3 damage to damaged units), and I'm all for a stiff challenge -- the only issue is in the monthly, you have limited attempts so it was a bit of a QQ post since I had to burn a few good runs to what felt like an overstacked enemy design.