The Leona changes were very bad for her

The goal was to make her late game better but at the cost of her early game, which is counter productive because she needed to bully the early game to transition in to the late game with a lead

Now that she cant bully nearly as well she is more likely to lose lane than bully it, which in turn makes her weak late game, so the changes are really pure nerfs.

Lets break it down, flat damage nerfs to her Passive, Q, W, and ultimate, in exchange for what?

Shorter CD on Q, well, if she doesnt make her first Q count shes probably a sitting duck and gonna die so thats not worth a damage nerf. She doesnt need the extra range so take that back and return the damage plz. Plus they fixed a bug that made her stun a bit longer than intended which is technically a nerf since shes had that for as long as I can remember.

What else, oh her E roots .25 seconds longer, big deal...

And now she has this really pointless on hit damage that is only active for 5 seconds after casting her biggest spell. So basically they made it so she needs to be in a vulnerable position/all-in every time she wants to make the full use of her ult.

Bad bad bad. revert revert revert. fix fix fix.

As far as im concerned Leona is more viable in a solo lane or jungle where she can just farm her way to the late game when she finally turns on.

As far as the supp role goes, too much risk for too little reward, t3 supp at best.