Let's compare the two since they have the same cost in
.
Dusk:
50% of creatures missing you
50% of weapon missing you
Average of blocking half damage taken
Procrastination:
creatures attack every other turn
100% of weapon attacks get through
More than half damage taken
However, procrastination has one advantage over dusk, and that is its delaying creatures. This especially becomes prominent if the opponent has creatures with abilities. Procrastination is better than dusk when faced against a FFQ, pharaoh, or grower deck.