Oh ive started seeing no champ deck players that just spam undying. Tried making one myself. It's disgustingly strong. Especially with cards like Ravenous butcher, Ancient Crocolith, Oblivious Islander and ruination. Don't even start with the stupid interactions with cards like Chronicler of Ruin, any card that can copy a unit and make it ephemeral.
For 10 mana, you can drop a undying, place a Chronicler of Ruin to kill one and revive it (which really makes another Undying) then 3 spell mana for splinter soul to spawn a ephemeral undying 1/1. beginning of next turn you have a 3/3, 2 2/2 and a CoR 3/3. 7 free damage every attack.
It wouldn't be a issue if more obliterate or remove text cards were available. Until then, Undying should only scale in attack on death or become a 1/2 or a 0/2. Doesn't make sense for it to scale in defense if it can't defend.