Different issue here. Since dungeons can only be done one time per day, there is no danger of overcentralizing gameplay, because you can only spend about 3 to 5 minutes a day there before being forced to move on. Were dungeons infinitely repeatable for tiny amounts of crafting materials and still the only place you could get them, this would be just as bad for the game for the same reasons.
This would be one way to solve that issue. I’d still rather them appear in literally any other game mode, but if I could spend 30 minutes per week treasure hunting and end up with 218 more diamonds I think this would probably be below the burnout threshold. However, since this would also significantly alter crafting paths without too much extra effort, I highly doubt it will happen.
What I was hoping for when crafting was announced was for a trickle-in of crafting resources as a result of basically any gameplay. But the hard-bottleneck looks like it is here to stay, since they have already monetized around it. I’m still holding out hope for other stuff to make its way into the crafting system, hopefully in a way that gives a consistent outlet to all the resources that dead end into endgame but is also accessible to everyone, just in different quantities.