Wizards' article explains that Fury is the worst offender by far thanks to its board clearing ability which "makes playing with creature decks nearly impossible"
But Mega Evolutions situation is different because the pull rates themselves are the primary driver, not just allocated product quantities
Disciple of Caelus Nin Five mana may seem expensive, but Disciple of Caelus Nin has some great things going on, as it shrinks the board to just a handful of permanents on each side of the field
If you cast it at a time a sorcery couldnt be cast, its sacrificed at the end step
Terra, Herald of Hope Rarity: Mythic Rare Card Type: Legendary Creature Human Wizard Power/Toughness: 3/3 Casting Cost: RWB Market Value: $1.59 (Regular), $1.32 (Foil) As much as I love Celes, there's a reason that Terra, Herald of Hope's value continues to rise weeks after the Final Fantasy Magic: The Gathering set's release
It's also probably good enough for Red Token decks, most notably Purphoros, God of the Forge