[Autumn]

I don't think its a singular stat spread really since you still need WIL or SKI in that regard, especially if you want to go for a hit mage which priests can absolutely do, there are a plethora of paths for offensive priests to follow, but I don't think denying them in that regard is any correct option either, they should have the necessary tools to deal damage, mage or otherwise. As if they don't then the offensive based priest characters become rather worthless in that regard, vice versa if you nerf the healing aspect of it.

[WaifuApple]

You can have variations, but they are optional based on flavour. I mean that a stat spread that isn't hard to achieve can give you potent healing and potent damage - and immunities come atop that because they work regardless of stats, making them pretty low effort. It's not healthy for balance to have one class line do so, so much without more drawback.

[Autumn]

Its not like priest damage is really insane unlike some more intended damage classes like Evoker's or Tactician's, Priest's damage is very average in comparison and befits more a defensive centered class, I'd say its damage potential is around the same as Hexer's which is quite generous, I think the only part where priests do significant damage is on a needle combo, which is actually really easy to avoid conventionally and has a cooldown.

[WaifuApple]

You're looking at it like the problem is something specific. It's how easy it is to combine those three things that is the issue. Which is why my suggestion didn't specifically nerf one specific thing. It was nerfing the combination but allowing them to exist seperately without being hit by that nerf. You can make your allies immune to status effects. You can heal them when they're running low. You can tank yourself up more with sanctuary, while bringing them down. And to add to that you can also damage the enemy. Even with skill slots to consider it's not difficult to do.