I tested all the previous set of changes last cycle and thought they were pretty good. Leona has been my main since early Season 4 (basically when I started playing League and I'm more of a one trick than anything at this point), and today's changes are terrible in comparison.
1. The new Incandescence effect does give Leona a bit more oomph and relevance after she uses her combo, but in this current build, the tradeoff is nerfs to her passive damage, Q damage, W damage, and now ult damage is drastically lowered. It seems a bit much that Leona has to give up her early bullying power just because at 6 and roughly every 90s AND provided you land your ult properly, you get a small powerspike that doesn't actually feel powerful even when the autos reapply sunlight, especially when your team is very behind. To cap things off, Incandescence doesn't feel as great compared to the last build before the changes were pulled last PBE cycle - the damage is reduced from before and you can't necessarily rely on your team to consecutively proc Sunlight for you.
2. Nerfing base damage is totally fine on champs that actually build damage, but why nerf Leona's base damage so hard? I'd say that 98% of Leona players normally play her as support, where she builds the standard tank and support items (FotM, Locket, Frozen Heart/Randuins/Sightstone/boots and whatever situational item to round it all out). She needs her base damage on her abilities and passive to actually be able to dominate lane, since as game length goes on, Leona's winrate decreases by quite a bit, as shown on op.gg's statistics on support Leona. Additionally, if Leona loses lane, it's extremely hard for her to come back unless the rest of her team carries. Even though my real account's in Silver, I've played plenty of higher level games and you can't always rely on your teammates to carry and proc Sunlight. Many times I've won 2v2s and teamifghts through Leona's base damage alone, but in the games I've played today, couldn't trade worth anything and previously where enemies should have died, they lived and I lost the trade and eventually lane. Losing base damage on supports actually hurts a lot.
3. Now, the good stuff is that the lower CD on Q is really good and with 40% CDR, you can stun every 3s in a teamfight. It's strong and feels good. Same goes to the E root duration buff. The snare feels more substantial and E -> R is pretty much guaranteed provided that you land E.
4. Leona hasn't been a priority pick in pro play since early Season 4 (I always get excited whenever she gets picked in a game nowadays), and has a low pick rate and average winrate in SoloQ/DynamicQ. I find her to be countered by more supports nowadays rather than countering them, and these changes don't seem to help as feeling as an overall nerf when she needs to be a little stronger to counter sustain supports (which may run rampant given the recent changes to support items boosting sustain).
**TL;DR:** Leona's current build makes her weaker than before because putting a new effect on her ult (that is easily dodgeable and missable) apparently merits nerfing her damage on everything else but E. Sure, she can CC more effectively, but her early bullying power is greatly diminished and makes her feel worse than last week's changes and currently on live servers. Last week's changes (Incandescence on ult, no MS on passive) felt a whole lot better than today's without making her OP. Thanks for reading and leave your thoughts below!