Confused by Magic the Gathering Arena trigger damage order (Revenge of Ravens)
Revenge of Ravens works correctly. It deals damage as soon as creatures attack, before they deal combat damage.
The combat phase is a multi-step process, it doesn't simply happen all at once. In the most simple terms, first the attacker declares the creatures which attack, then the defender declares the blocking creatures, then creatures deal combat damage.
Between each of these steps, players can cast spells, and abilities like ROR can trigger and resolve. ROR triggers on that first step, when creatures attack, so it can absolutely kill the attacking player before any of their creatures can deal combat damage.

506.1. The combat phase has five steps, which proceed in order: beginning of combat, declare attackers, declare blockers, combat damage, and end of combat.

The priority system determines which player, if any, can cast spells and activate abilities. The priority system also determines when spells and abilities on the stack resolve.

117.3a The active player receives priority at the beginning of most steps and phases,