From what I understand, the main criticism about the new dragonite system does not seem to be that much, that it is based on random chances, but that it involves the soulforge as an otherwise (mostly) non-random entity.
So why not circumvent the issue by making dragon hoards a third type of vault fight? Same entry cost of 500 dragonite, three regular gnomes, or even Cedrics, if you want, headed by Diamantina, and you get an egg drop.
I see far less complaints from people not getting the tarot card they wanted, compared to hatched dragons, despite the core problem being the same.