That may be true for Standard. I wouldn’t mind if they received some love if Standard was my thing, 'cause as you say they are losing some big cards.
But in Wild they will get a huge peak of annoyance. Their spellstone, plus the new spell that is just a new spellstone, plus Catrina… past turn 6 they will not care using these to ressurrect only one big minion (Lich king, Ragnaros, statue?), since the next one it will ressurrect one extra copy, and the next one two extra copies, and when you can’t kill all copies in a single turn (and you are still fighting for your life), Catrina will put a constant flow of new copies, and removing her will not be an option since she will be with all the remaining copies that survived last turn.
And that is the most soft scenario in which the Big Priest only played 1 minion at earlier turns with Barnes or Shadow Essence. If he had 2 different minions pre-late game, it will be twice or three times as horrible, specially if they were able to use the 2 and 4 mana ressurrections before late-game.
Yeah, Big Priests can die to very aggresive decks. But pure aggresiveness is not my style, so I openly admit that they are my direct counter. That doesn’t disallow me to point out the lack of balance in their difficulty-to-play/power; if you are alive past turn 6 as Big Priest, snowballing exponentially is a matter of having the right card in your hand each turn. Nothing complex about it.