Leona is a very risky tank, because she doesn’t have any tools for disengaging. When she goes in, she’s either getting her own lane killed or she’s killing the enemy—with no middle ground.
To increase her powers of peeling and the mayhem she can cause when she does go in, she’s getting some pretty big buffs. For starters, her passive, Sunlight, will now deal much more damage when procced. The Sunlight will last for less time on her targets, though, to compensate.
Her stun, Shield of Daybreak, is getting a reduced cooldown, as well. Instead of starting the game at nine seconds and ending at five, it will have a six second cooldown throughout the entire game. Early game trades are going to be much more devastating, because she’ll be able to use her stun multiple times per fight.
These buffs for Leona will be available with next patch 7.17 in few weeks only.