Reference (SimulationCraft and Icy Veins)

Reference only, off by default: the optimal Devastation priority. Procs, cooldowns and the target's burn are hidden in Midnight combat, so it cannot run there; read it, or clone it to experiment. Pulls with Living Flame. Scalecommander (Mass Disintegrate known): Eternity Surge, Fire Breath, Deep Breath on two or more enemies, Disintegrate with Mass Disintegrate charges, Pyre on five or more, Disintegrate, Living Flame on Burnout with Leaping Flames, Unbound Flame below two Essence Bursts, Azure Sweep. Flameshaper: Eternity Surge, Fire Breath when its burn is missing or ending, Pyre on five or more, Disintegrate, Deep Breath on four or more, Unbound Flame, Living Flame on Burnout with Leaping Flames, Azure Sweep. Then Azure Strike while moving, Living Flame, Azure Strike. Use empowers at rank 1 on one target (Icy Veins). Reminders: Dragonrage, Tip the Scales in Dragonrage or with Fire Breath ready, Deep Breath for Scalecommander, plus the utility reminders.

Adapted from SimulationCraft default action list: Devastation, Icy Veins: Devastation Evoker rotation (12.1.5).

In game: /rm set devastation-guide chooses it by hand; it loads only for its edition and class, and is listed only for the specializations it is for. It ships disabled: an alternative to the recommended rotation for its specialization. Turn it on in game (Rotations, then Enabled) and either turn the other off or give this one a higher priority.