* The Birth of Meletis originally gained life based on the greatest toughness among creatures you control, but that made things too swingy with aggro decks. Either they destroyed the wall and you gained no life, or they couldn't and you gained control of the game.
* All demigods originally had power based on devotion, but that was too powerful for the ones that cost two mana. They considered weakening them by making them cost 1M (M = colored mana) instead of MM, but instead they made their toughness be based on devotion.
* With Shatter the Sky, it seems like four-mana wraths are here to stay. They decided Wrath of God is too strong, but there's plenty of room for wraths weaker than it at four mana.
* Elspeth Conquers Death originally returned only a creature or an Elspeth planeswalker with the last ability, but it was changed to any planeswalker. They realized the similarities with The Eldest Reborn, and tried to make sure it didn't come off as a weaker version of it.
* Elspeth, Sun's Nemesis had escape and all minus abilities from the start. It previously had the current set of abilities but 4 loyalty, and they actually weakened it by giving it 5 loyalty. Previously, the play pattern of make tokens -> make tokens -> escape -> make tokens was too strong, and now you have to do something else in between.
* Shimmerwing Chimera was originally a direct enchantment-shifted version of
Esperzoa, but that proved to be much stronger in this environment than in Alara.
* Ashiok's Erasure was designed to hose escape-based decks, with it countering "can't be countered" to make it a bit more playable.
* Hateful Eidolon's ability was originally on Tyramet, but they decided to make it a build-around for white-black instead of just monoblack. It was also an aggro card with some trinket text, but they adjusted the stats to make the aura part more significant.
* Woe Strider could originally sacrifice itself, and got two goats on escape but none on normal enter. They decided to give it a single goat whenever it entered, so it felt good to cast it normally instead of making it a race to get it into the graveyard.
* Nightmare Shepherd was originally symmetrical. Whenever any nontoken creature died, its controller made a 1/1 Nightmare. However, it got +1/+1 for every Nightmare on the battlefield. This made things too grindy, so now it only brings back your own stuff and doesn't have the tribal effect.