Killing with Divine Deflection
The oracle rulings of Divine Reflection state:

If Divine Deflection prevents damage, excess damage (if any) dealt by
that source is dealt at the same time. Immediately afterward, as part
of that same prevention effect, Divine Deflection deals its damage.
This happens before state-based actions are checked, and before the
spell or ability that caused damage to be dealt resumes its
resolution.

So, the damage is done at the same time and only after are state-based actions checked.

704.5. The state-based actions are as follows:
704.5a If a player has 0 or less life, he or she loses the game.

As checking the life totals is a state-based action, both players will have 0 life at the same check, thus the game ends in a draw!