I'm not sure I'm entirely satisfied to be honest. The concept of a female tank was great, but she doesn't look like much of a tank of a tank to me. When they described her, I believe Phreak's words were, "Leona is a pure tank".
However, Leona doesn't appear to be much of a tank. She just seems like a another tanky-dps hybrid to me. 4/5 of this Champion Spotlight was Phreak chasing away from his team to go single out an opponent for a slay. Also, what happened to her 'Soft Taunt'?..
In my opinion, her Eclips (AoE Shield>Damage) should be adjusted. It is just a beefed version of Jarvan's shield. This doesn't really provide any sort of a taunt at all, if anything it currently just promotes you not being focused and enemies running away from you to avoid the damage.
I had an idea of how they could adjust her AoE to make her have a little more tank utility...
Eclipse: Upon activation, Leona receives X bonus armor and X bonus magic resistance for 3 seconds. An explosion of damage will occur after the initial 3 seconds, dealing less damage based on how much damage Leona receives over the 3 seconds. <- This would create an actual 'soft taunt', it would promote targets to focus you to reduce your AoE team damage. This would help tip the scales to turn Leona into more of a tank, and less of a tanky-dps.
* Message to the downvoters.. Sorry you just want another OP tanky-dps to continuing ganking with. Some of us actually care about the other roles in the game, rather than just carrying.