Ember Archers are the utility damage of the Phoenix Elves. Do not count on them as straight-out combat units as they are not very efficient cost wise. Don't expect to win ranged wars with them.
Their power rests on the ability to to do 1 damage without even attacking, just moving. This is important for the Phoenix Elves as they do a lot of circumstantial damage and often enemy units are left with just 1 life. The Ember Archers are great to finish them off without having to use an attack. Often allowing you to attack a unit that was being protected with just a 1 life unit.
Having said that, they are still good to use in "Maldaria's cycle", and they are quite efficient in Spirit of the Phoenix turns.