Square Enix finally released a Final Fantasy XIV Piano Collections this spring. The two-disc set includes all six "A Realm Reborn" piano arrangements from the album "From Astral to Umbral", all six "Heavensward" piano arrangements from the album "Duality", and five arrangements new to this collection - one from "Heavensward" and four from "Stormblood".

I haven't given many listens to the Duality or new tracks yet, but just having the excellent From Astral to Umbral piano arrangements separate from that album's rock tracks (not to mention available on CD instead of Blu-ray) makes this worth considering.

Quick addendum that the five once-exclusive arrangements not on "From Astral to Umbral" or "Duality" are now available on the just-released "Journeys: Final Fantasy XIV Arrangement Album", which similar to those other two albums is a half piano, half rock arranged album. For people who like those albums' rock arrangements (and don't mind the Blu-ray or digital download formats), that would probably be the way to go over FFXIV Piano Collections.