Paying 3 for Negate isn't great either
Even just being able to find a Dragon more reliably can make a big difference and Dig Through Time gives us a lot of looks
At the prodigiously huge cost of 13 Mana, Emrakul at first seems too unwieldy to be practical, but this cost is reduced for having a stacked graveyard
The contents of Azurite Sea were revealed two months ahead of its arrival which hopefully means we'll find it more about it this month, maybe after the Moana 2 promo comes to an end.
However a few do have "practical" uses - here are some examples: The particular card you reference, Garruk the Slayer, was created for the Magic 2015 prerelease and is used in a variant where one player plays normally and the other plays as Garruk
Nibelheim Aflame is, instead, just a very flashy Commander card