Rewind records raid-wide damage taken over the prior 5-second window and then heals the raid back for a portion of that amount over the next 5 seconds. The bigger the damage event leading into the cast, the bigger the heal pool.

It has a 40 yard range, which is wider than the evoker's usual healing range.

Heal absorbs do not count as damage taken, so casting Rewind to counter absorb mechanics is wasted.

The best windows for Rewind are ones with heavy damage in the 5 seconds before the cast (to build a large pool) followed by more incoming damage during the 5-second active heal portion, so the healing isn't overhealing.

Slot it onto those damage patterns specifically. With Temporal Artificer talented it comes back every 3 minutes, so plan it for the highest-impact damage events on that cycle.