Ral has been the worst of the cube planeswalkers for a long time; Saheeli acts as redundancy for Young Pyro with some occasional upside.
Ral Zarek > Saheeli, Sublime Artificer

The top 3 changes are basically just more efficient/playable cards that fill the same role. The bottom two are attempts to make Orzhov more appealing - replacing Ayli with a solid cheap exile effect for cube bombs and the very slow Blood Baron with an interesting tokens/aggro combo card.
Coralhelm Commander > PteramanderRattleclaw Mystic > Paradise DruidKrosan Grip > Return to NatureBlood Baron of Vizkopa > Cruel CelebrantAyli, Eternal Pilgrim > Despark

Sigarda, Heron's Grace > Trostani Discordant

More Gruul changes

More beating with big beasties
Clan Defiance > Xenagos, God of RevelsThrash // Threat

Ravnica Allegiance changes

Ammit Eternal > Pestilent SpiritBrute Force > Light Up the StageNiblis of Frost > Sphinx of ForesightZhur-Taa Druid > Rhythm of the WildXenagos, the Reveler > Domri, Chaos BringerOlivia Voldaren > Judith, the Scourge DivaTrygon Predator > Gyre Engineer

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