Leona really deserves significant changes.
Q-Increase its damage at rank lower ranks, also cause it to heal Leona for 3/3.5/4/4.5/5% of her max health. Targets killed by Q increase Leonas Armor by a small amount. Permanently.
W- Leave its damage, and stats the same. Give it a sunfire effect, scaled properly to not be as strong as a free sunfire cape during laning phase.
E- When Zenith Blade connects to a target, it should give her a absorb that functions and is tuned exactly how Jarvans absorb is.(without the slow).
R leave it it exactly the same.