Rewards for tier 3 are underwhelming imo. I would rather have 3-8 rare candies than a likely trash gible/scyther/dratini/bunnelby.
I'd say tier 3 rewards only for hard but you get to chose the nature or ability of the pokemon in the egg. Either nature or ability. Maybe both? As a third time?
It would give a nice touch of real pokemon breeding in which you can also manipulate the egg.