Let’s first look at the lore of resurrection effects in fantasy novels and movies, and in games such as Dungeons and Dragons. (I don’t know WoW so I don’t know if resurrection exists there and if so, how it works).
When you want a dead team mate resurrected, you bring their body to a high level priest, they do some crazy difficult incantations that take a lot of time and some very expensive ingredients, and then life returns to the dead body. That’s at least how it works in the D&D versions I know of.
In novels and movies, the effort and price of resurrection may be different but they, too, always return the soul to the dead body and revive it. No dead body means no resurrection.
What all these effects have in common is that no copies are made. Once you are back in this life, you cannot be resurrected again - at least not until your next death. And that also makes sense from a linguistic point of view, the roots of the word show that a dead body is returned to life, not that a new body is created.
So what does this mean for the game? I think that resurrect would be both more logical from a lore and linguistics point of view AND more balanced if it was implemented by moving a minion from the graveyard zone back onto the board, instead of copying a minion from the graveyard as it does now.
The effect would still be pretty strong. You can still force me to kill Ragnaros again and again, turn after turn. But at least you cannot get two or more copies of Ragnaros, or of Catrina Muerte - at least not by resurrection alone.
You would still be able to generate copies in a different way. And once there are two copies of Ragnaros on the board and I kill both, there are two copies in the graveyard, so now you can also resurrect two in a single turn (but not three).
It would be a nerf to all resurrect cards, and it would be hard to defend doing this without granting full dust refund on all resurrect cards. Which is why I think Blizzard will be hesitant to do this. But on the other hand, they prove expansion after expansion that they really like the resurrect mechanic for the Priest class, and this small change would probably allow many more interesting interactions and designs without breaking game balance too much.
My biggest problem with Resurrect Priest as an archetype in general is that it is a very binary draw-dependent archetype. Coining Barnes turn 3 to pull Y’Shaarj to pull another big boy with one or two resurrect spells in hand wins you the game. Drawing all big minions in your opening hand and finally finding Shadow Essence turn 7 to get a 5/5 Barnes on the board loses the game. It feels like there is no middle ground. The game will (almost) always result in one player feeling there is nothing they can do to stop the onslaught, and the other player getting a win without doing much effort.
In other words: the problem with Resurrect Priest is not game balance related, it is that it saps the fun out of the game.