Eden’s Promise: Eternity (Savage) - Oracle of Darkness
You may want to consider holding the first Swiftcast slightly to avoid a scenario where because of incorrect mana levels, you can not finish your melee combo before the first Darkest Dance knockback.
While you can still use this Swiftcast early, keep a close eye on your mana levels as you do so.
Buffs After Relativities
Both your Manafication and Embolden should be held until after every relativity mechanic resolves, to align each with party buffs consistently.
During Single Apocalypse, you will likely have enough mana for a melee combo after the large jump AOE. You can safely dualcast your way through the center here and perform a melee combo on the boss before the rotating AOEs begin.
Potion And Double Melee Timings
Aim to cap both of your gauges at 100 | 100 Black and White mana heading into Advanced Relativity to perform a double combo afterwards.
After the final Rewind resolves, there will be a moment where the boss is still untargetable. Use this chance to prepare a Dualcast using Vercure, allowing you to instantly cast a Verthunder or Veraero and weave your pot before starting your two melee combos.
Triple Apocalypse Uptime
Full uptime can be kept during Triple Apocalypse with proper Swiftcast usage.
Additionally, depending on where your tank baits the initial jump, a safe spot may exist that does not require you to move back center.